I have been working with Processing for a long time under Windows and Ubuntu and I have never found any problem. I was happy with 10.04 but, after install Ubuntu 11.04 x64, Processing start to show me some errors. 

After installing the OpenJDK, instead of Sun's, every thing works well except that I cannot "Save as..." any new sketch. This is the error message that I get:

 java.lang.NullPointerException: NullPointerException

at sun.awt.motif.MFileDialogPeer.setFont(Native Method)

...

I search for a solution, but I did not find any similar problem. I am using Ubuntu 11.04 x64 and Processing 1.5.1.

Any help will be very appreciated. Thank you very much.