If you move aside your /etc/X11/xorg.conf are you still able to reproduce the freeze?
When the system is frozen, can you ssh into the computer? If so, please collect 'sudo dmesg > dmesg.txt' and your /var/log/kern.log and attach to this bug report.
Also, which screensaver package are you using? The 3D screensavers were removed from the version of GNOME included in 12.04; are you using xscreensaver?
No errors in any of the log files.
If you move aside your /etc/X11/xorg.conf are you still able to reproduce the freeze?
When the system is frozen, can you ssh into the computer? If so, please collect 'sudo dmesg > dmesg.txt' and your /var/log/kern.log and attach to this bug report.
Also, which screensaver package are you using? The 3D screensavers were removed from the version of GNOME included in 12.04; are you using xscreensaver?