X interface lockup on exit

[Nicholas Ritter]

I have a dual AMD Opteron system with an ATI Fire X2 card. My X server 
is using the Vesa driver, because the X2 ATI card does not have a driver 
available for 2.6 64bit yet. While using the X interface in Fedora Core 
2, if I exit to the shell from gnome the interface locks up, and a 
control-alt-delete fixes it after the gracefull reboot.

Is there any idea what could be causing this?

Nicholas