I don't have any problem using ortho() and OPENGL renderer (except the ones from the google code issue).
Are you using processing 1.2.1 ? 

Or let us know about your sketch that give you that error.

OpenGL has a native function to deal with orthographic projection ( glOrtho) but that might be a bit advanced for now.
Seems the issue is gonna be fixed soon anyway, so next release of processing should fixed it.
Andres must know more about this subject

Well, in between I have changed the sketch a bit so I don't have this error message anymore...

...but with ortho() I don't have anything on my screen at all !

1. //
2. // Grid creation with rows x cols points. Plane is set in an OpenGL 3D scene. Intersections can be moved.
3. //
4. import controlP5.*;
5. import processing.opengl.*;
6. import codeanticode.glgraphics.*;
7. import javax.media.opengl.*;
8. import javax.media.opengl.glu.*;
9. import java.nio.*;
10. //import remixlab.proscene.*;
11. // Variables
12. int rows = 15; // number of rows
13. int cols = 8; // number of cols
14. int points = rows * cols ; // number of points
15. int x_size = 500; // width
16. int y_size = 500; // height
17. int margin = 50; // margin
18. int button_height = 100; // additional height for button zone
19. int bgColor = color(255, 255, 255); // background color
20. int squareColor = color(128, 0, 0); // square color upon mouse over point
21. PVector[] mesPoints = new PVector[points];
22. PVector[] fixedPoints = new PVector[points]; // unmovable points
23. // Mouse var
24. boolean bover = false;
25. boolean locked = false;
26. int movingPoint = -1 ; // number of selected point
27. int mouseDX = 0;
28. int mouseDY = 0;
29. int oldMouseX = 0 ;
30. int oldMouseY = 0 ;
31. // this is only a note.
32. // we will not use variable b in the code below.
33. // we have to use controlP5.Button here since there
34. // would be a conflict if we only use Button to declare button b.
35. //Button
36. ControlP5 controlP5;
37. controlP5.Button b ;
38. // a button-controller with name buttonValue will change the
39. // value of this variable when pressed.
40. //int buttonValue = 0;
41. GL gl;
42. GLU glu;
43. //********** SETUP
44. void setup()
45. {
46.   //ortho();
47.   smooth();
48.   ellipseMode(CENTER);
49.   rectMode(CENTER);
50.   size(x_size+200, (y_size+button_height+200), OPENGL);
51.   background(bgColor);
52.   //CONTROLS
53.   controlP5 = new ControlP5(this);
54.   controlP5.addButton("Bouton1",0,50, (y_size+50),88,21);
55.   controlP5.setColorActive(color(255, 0, 0)); // color for mouse-over
56.   controlP5.setColorBackground(color(128, 0, 0)); // default background color
57.   controlP5.setColorLabel(color(255, 255, 255)); // text color
58.   //controlP5.controller("Bouton1").setLabel("Regenerate points"); // button label
59.   //Creates positions for unmovable points
60.   for (int i = 0; i < rows; i++) {
61.     for (int j = 0; j < cols; j++) {
62.       int current_point = (cols * i)+j;
63.       fixedPoints[current_point] = new PVector( ((((x_size - (2*margin))/(cols-1)) * j)+margin), ((((y_size - (2*margin))/(rows-1)) * i)+margin), 0);
64.     }
65.   }
66.   // Creates positions for movable points
67.   for (int i = 0; i < rows; i++) {
68.     for (int j = 0; j < cols; j++) {
69.       int current_point = (cols * i)+j;
70.       mesPoints[current_point] = new PVector( ((((x_size - (2*margin))/(cols-1)) * j)+margin), ((((y_size - (2*margin))/(rows-1)) * i)+margin), 0);
71.     }
72.   }
73. }
74. //********** DRAW
75. void draw()
76. {
77.  
78. PGraphicsOpenGL pgl = (PGraphicsOpenGL) g; // g may change
79. GL gl; // = pgl.beginGL(); // for mouse to world conversion
80. GLU glu = pgl.glu ; // same here
81.   // Erases everything  - redraws lines
82.   background(bgColor);
83.   //Open GL 3D stuff
84.   lights();
85.   translate(0, 350);
86.   rotateZ(map(-180, 0, height, 0, PI));
87.   //---- Draw lines for unmovable points
88.   strokeWeight(2);
89.   stroke(0, 0, 0);
90.   for (int i = 0; i < rows ; i++) {
91.     for (int j = 0; j < cols ; j++) {
92.       int current_point = (cols * i)+j;
93.       //Draw horizontal lines
94.       if (j < cols - 1) { // all but last column
95.         beginShape(LINES);
96.         vertex(fixedPoints[current_point].x, fixedPoints[current_point].y, fixedPoints[current_point].z);
97.         vertex(fixedPoints[current_point+1].x, fixedPoints[current_point+1].y, fixedPoints[current_point].z);
98.         endShape(); 
99.       }
100.       //Draw vertical lines
101.       if (i < rows - 1) { // all but last line
102.         beginShape(LINES);
103.         vertex(fixedPoints[current_point].x, fixedPoints[current_point].y, fixedPoints[current_point].z);
104.         vertex(fixedPoints[current_point+cols].x, fixedPoints[current_point+cols].y, fixedPoints[current_point].z);
105.         endShape();
106.       }
107.     }
108.   }
109.   //---- Draw lines for movable points
110.   for (int i = 0; i < rows ; i++) {
111.     for (int j = 0; j < cols ; j++) {
112.       int current_point = (cols * i)+j;
113.       //Draw horizontal lines
114.       if (j < cols - 1) { // all but last column
115.         if ((i == 0) || (i == (rows - 1))) { // first and last rows
116.           stroke(0, 0, 0); // outer lines are black
117.         } else {
118.           stroke(0,192,255); // inner lines are blue
119.         }
120.         beginShape(LINES);
121.         vertex(mesPoints[current_point].x, mesPoints[current_point].y, 0);
122.         vertex(mesPoints[current_point+1].x, mesPoints[current_point+1].y, 0);
123.         endShape();
124.       }
125.       //Draw vertical lines
126.       if (i < rows - 1) { // all but last line
127.         if ((j == 0) || (j == (cols - 1))) { // first and last column
128.           stroke(0, 0, 0); // outer lines are black
129.         } else {
130.           stroke(0,192,255); // inner lines are blue
131.         }
132.         beginShape(LINES);
133.         vertex(mesPoints[current_point].x, mesPoints[current_point].y, 0);
134.         vertex(mesPoints[current_point+cols].x, mesPoints[current_point+cols].y, 0);
135.         endShape();
136.       }
137.     }
138.   }
139.   // Draws points
140.   strokeWeight(1);
141.   for (int i = 0; i < (rows * cols) ; i++) {
142.     if ( (i % cols == 0) || (i % cols == (cols - 1)) || (((i+1) / cols)  == 0) || (((i+1) / cols)  == rows - 1 ) ) { //outer points
143.       stroke(0,0, 0);
144.       fill(0,0,0);
145.     } else { // inner points
146.       stroke(0,192, 255);
147.       fill(255,255,0);
148.     }
149.     ellipse(mesPoints[i].x, mesPoints[i].y, 10, 10);
150.   }
151.  
152.  
153.   //Tests whether mouse rolls over points and draws red squares
154.     strokeWeight(1);
155.     if (locked) {
156.       squareColor = color(255, 0, 0);
157.     } else {
158.       squareColor = color(128, 0, 0);
159.     }
160.     stroke(squareColor);
161.     fill(squareColor);
162.     if (!locked) {
163.       for (int i = 0; i < points; i++) {
164.         // distance between mouse pointer and projection of underneath vertice on screen.
165.         if(dist(mouseX, mouseY, screenX(mesPoints[i].x, mesPoints[i].y, mesPoints[i].z), screenY(mesPoints[i].x, mesPoints[i].y, mesPoints[i].z)) <= 5) {
166.           movingPoint = i;
167.           rect(mesPoints[i].x, mesPoints[i].y, 10, 10);
168.           i = points ; //not necessary to go on with loop
169.         } else {
170.           movingPoint = -1;
171.         }
172.       }
173.     }
174.       if (movingPoint != -1) {
175.         bover = true ;
176.       } else {
177.         bover = false;
178.     }
179.     pushMatrix();
180.     translate(0, -350);
181.     rotateZ(map(0, 0, height, 0, PI));
182.     controlP5.controller("Bouton1").setLabel("Regenerate points"); // button label
183.     popMatrix(); // disabled otherwise problem with point dragging
184.    
185. }
186. // DRAW FUNCTION FINISHED HERE
187. //********** Detects whether mouse button is pressed
188. void mousePressed() {
189.   if(bover) {
190.     locked = true;
191.   } else {
192.     locked = false;
193.   }
194. }
195. //********** Moves selected point while button held
196. void mouseDragged() {
197.     if(locked) {
198.       stroke(squareColor);
199.       fill(squareColor);
200.       rect(mesPoints[movingPoint].x, mesPoints[movingPoint].y, 10, 10);
201.       mouseDX = mouseX - oldMouseX;
202.       mouseDY = mouseY - oldMouseY;
203.       oldMouseX = mouseX;
204.       oldMouseY = mouseY;
205.       strokeWeight(1);
206.       stroke(255,0,0);
207.       fill(255,0,0);
208.       mesPoints[movingPoint].x = getMouse3D()[0] ;
209.       mesPoints[movingPoint].y = getMouse3D()[1] ;
210.       mesPoints[movingPoint].z = getMouse3D()[2] ;  // mouse (screen) to world conversion
211.     }
212. }
213. //********** Unlocks upon button release
214. void mouseReleased() {
215.   locked = false;
216.   bover = false;
217. }
218. //**********function Bouton1 will receive changes from
219. //********** controller with name controlP5
220. public void Bouton1(int theValue) {
221.     for (int i = 0; i < rows; i++) {
222.       int randomX;
223.       int randomY;
224.       int randomZ;
225.       for (int j = 0; j < cols; j++) {
226.         int current_point = (cols * i)+j;
227.         if ( (current_point % cols == 0) || (current_point % cols == (cols - 1)) || (((current_point+1) / cols)  == 0) || (((current_point+1) / cols)  == rows - 1 )) { //outer points
228.           randomX = 0;
229.           randomY = 0;
230.           randomZ = 0;
231.       } else { // inner points
232.         randomX = int(random(-10, 10));
233.         randomY = int(random(-10, 10));
234.         randomZ = int(random(0, 40));
235.       }
236.       // mesPoints[current_point] = new PVector( ((((x_size - (2*margin))/(cols-1)) * j)+margin+randomX), ((((y_size - (2*margin))/(rows-1)) * i)+margin+randomY), randomZ);
237.       mesPoints[current_point] = new PVector( ((((x_size - (2*margin))/(cols-1)) * j)+margin+randomX), ((((y_size - (2*margin))/(rows-1)) * i)+margin), randomZ);
238.     }
239.   }
240. }
241. //************* SCREEN TO WORLD FUNCTION - found on old Processing forum ********************
242. float[] getMouse3D()
243. {
244.   ((PGraphicsOpenGL)g).beginGL();
245.   int viewport[] = new int[4];
246.   double[] proj=new double[16];
247.   double[] model=new double[16];
248.   ((PGraphicsOpenGL)g).gl.glGetIntegerv(GL.GL_VIEWPORT, viewport, 0);
249.   ((PGraphicsOpenGL)g).gl.glGetDoublev(GL.GL_PROJECTION_MATRIX,proj,0);
250.   ((PGraphicsOpenGL)g).gl.glGetDoublev(GL.GL_MODELVIEW_MATRIX,model,0);
251.   FloatBuffer fb = ByteBuffer.allocateDirect(4).order(ByteOrder.nativeOrder()).asFloatBuffer();
252.   ((PGraphicsOpenGL)g).gl.glReadPixels(mouseX, height-mouseY, 1, 1, GL.GL_DEPTH_COMPONENT, GL.GL_FLOAT, fb);
253.   fb.rewind();
254.   double[] mousePosArr=new double[4];
255.   ((PGraphicsOpenGL)g).glu.gluUnProject((double)mouseX,height-(double)mouseY,(double)fb.get(0),model,0,proj,0,viewport,0,mousePosArr,0);
256.   ((PGraphicsOpenGL)g).endGL();
257.   return new float[]{(float)mousePosArr[0],(float)mousePosArr[1],constrain((float)mousePosArr[2], 0, 100)};
258. }
259. //*********
260. // END
261. //*********

The missing method warning is because you are calling ortho() before size(). You should call ortho() inside draw() instead:

Hi, I was just referring to the behavior oddities reported in the google code issue.