I have the same problem with the nvidia-glx driver. Occours in Mozilla-firefox and Mozilla-thunderbird apps.
I'm using a nVidia GeForce 7300 GS, but I had installed before an ATI vga card. -- Strange artifacts in text fields within web applications when moving cursor with keyboard https://launchpad.net/bugs/50768 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
