Comment 14 for bug 669535

I did more testing on my box. With the box in an idle state (~0% CPU load), I used a hitch-detection script (it prints a "hitch" error to stdout every time the system goes more than two seconds without scheduling the script) to try the following:

After sudo /etc/init.d/gdm stop, and logging in at the text console (ctrl-alt-F1), the script still reported hitches, so the issue would not seem to be X-related.

Still on the text console, /etc/init.d stopping apache2, ntop, mysql, ntpd, had no effect, I still saw hitches.

Switching into single-user mode (sudo telinit 1, choose without networking) had no effect, I still saw hitches.

During a hitch, tapping the ctrl key was enough to immediately wake the system back up (causing the hitch to be reported by the script).

After restarting gdm, I tried uninstalling Sun VirtualBox, but I still saw hitches.

I found an old Ubuntu 9.10 CD and booted up from that. No hitches detected after 30 minutes.