Same problem,it only began when I enabled the desktop effects via the System > Preferences menu. In order to get this to work, I installed Xgl as recommended in http://ubuntuforums.org/showthread.php?t=488385
However, I did not install Beryl or Fusion, so it would seem that the problem for me was either triggered by installing Xgl or by enabling the Desktop Effects in 7.04
Same problem,it only began when I enabled the desktop effects via the System > Preferences menu. In order to get this to work, I installed Xgl as recommended in http:// ubuntuforums. org/showthread. php?t=488385
However, I did not install Beryl or Fusion, so it would seem that the problem for me was either triggered by installing Xgl or by enabling the Desktop Effects in 7.04