I can verify that for me the issue was the deprecated i810 driver. I had upgraded from Feisty (where my laptop didn't suffer this problem) to Gutsy, but because I had manually changed xorg.conf a long while back (for an unrelated issue), Xorg continued to use the i810 driver.
to automatically update my xorg.conf (as suggested in the file itself) straightened out my xorg setup and my computer hasn't exhibited the freezing behaviour since.
I can verify that for me the issue was the deprecated i810 driver. I had upgraded from Feisty (where my laptop didn't suffer this problem) to Gutsy, but because I had manually changed xorg.conf a long while back (for an unrelated issue), Xorg continued to use the i810 driver.
Running:
sudo dpkg-reconfigure -phigh xserver-xorg
to automatically update my xorg.conf (as suggested in the file itself) straightened out my xorg setup and my computer hasn't exhibited the freezing behaviour since.