Characters typed in an xterm get corrupted.
This is caused by a bug in the Compiz package. Compiz provides special window manager effects when using hardware accelerated OpenGL.
To eliminate the corruption perform one of the following:
1) Disable visual effects:
Select System->Preferences->Appearance from the menu. Click on the Visual Effects tab. Select None.
2) Perform a package update. The latest Compiz package has a fix for this problem.
You may still want to disable Visual Effects for maximum compatibility.