I am using Ubuntu 11.10 with Gnome shell in my Inspiron e1505 laptop.

Intel Core 2 Duo Processor T7200
ATI X1400 graphics card

My problem is frequently, the screen freezes completely. Only the mouse pointer can be moved, no click or other interactions. Restarting gnome-shell or display manager does not fix the problem. I have to reboot system to clear the problem.

I tried gdm instead of lightdm and the problem is the same.

To try my luck, I installed 12.04 alpha and the problem is still there.

Although, when I used Fedora in the same laptop, I didn't have the problem.(but I prefer to stick to Ubuntu)

Please any suggestions or solutions.