It looks like inside of 
               PApplet.java this is how dataPath() is implemented. 
              
              

               Obviously tinkering with this code may help you. Just copy/paste this into your sketch,
              
              

               and this code will override default processing dataPath() method. 
              
              

               

              
              

               Now you can stick many 
               println() inside of 
               dataFile() to see which exactly call is
              
              

               returning faulty path.
              
              

               Or maybe someone better with Java can spot the error straight away just by looking at the code.
              
              

               

              
              

               

              
              

               

              
              

               

              
              

                
               public 
               String 
               dataPath
               (
               String 
               where
               ) 
               {
              
              

                   
               return 
               dataFile
               (
               where
               ).
               getAbsolutePath
               ();
              
              

                 
               }
              
              

               

              
              

               

              
              

                 
               /**
              
              

                * Return a full path to an item in the data folder as a File object.
              
              

                * See the dataPath() method for more information.
              
              

                */
              
              

                 
               public 
               File 
               dataFile
               (
               String 
               where
               ) 
               {
              
              

                   
               // isAbsolute() could throw an access exception, but so will writing
              
              

                   
               // to the local disk using the sketch path, so this is safe here.
              
              

                   
               File 
               why 
               = 
               new 
               File
               (
               where
               );
              
              

                   
               if 
               (
               why
               .
               isAbsolute
               ()) 
               return 
               why
               ;
              
              

               

              
              

                   
               String 
               jarPath 
               =
              
              

                     
               getClass
               ().
               getProtectionDomain
               ().
               getCodeSource
               ().
               getLocation
               ().
               getPath
               ();
              
              

                   
               if 
               (
               jarPath
               .
               contains
               (
               "Contents/Resources/Java/"
               )) 
               {
              
              

                     
               // The path will be URL encoded (%20 for spaces) coming from above
              
              

                     
               // http://code.google.com/p/processing/issues/detail?id=1073
              
              

                     
               File 
               containingFolder 
               = 
               new 
               File
               (
               urlDecode
               (
               jarPath
               )).
               getParentFile
               ();
              
              

                     
               File 
               dataFolder 
               = 
               new 
               File
               (
               containingFolder
               , 
               "data"
               );
              
              

                     
               return 
               new 
               File
               (
               dataFolder
               , 
               where
               );
              
              

                   
               }
              
              

                   
               // Windows, Linux, or when not using a Mac OS X .app file
              
              

                   
               return 
               new 
               File
               (
               sketchPath 
               + 
               File
               .
               separator 
               + 
               "data" 
               + 
               File
               .
               separator 
               + 
               where
               );
              
              

                 
               }
              

println("user.dir : " + System.getProperty("user.dir") );
println("Sketch path: " + sketchPath);
println("Sketch data: " + dataPath(""));

exit();

println( javaVersionName );
println( System.getProperty("java.home") + "\n");

println( System.getProperty("os.arch") );
println( System.getProperty("os.name") );
println( System.getProperty("os.version") + "\n");

println( System.getProperty("user.home") );
println( System.getProperty("user.dir") );
println( dataPath("") );

exit();