What's the output of the following commands:
Code:
cat /etc/X11/xorg.conf
as well as
Code:
cat /var/log/Xorg.0.log | grep EE
and
Code:
cat /var/log/Xorg.0.log | grep WW
If you're using Gnome, you might want to consider a more lightweight window manager like xfce4 or WindowMaker and see if that helps - you computer just might not be powerful enough to run the latest and greatest smoothly.