Comment 490 for bug 993187

I had the problem too:

Complete system hang, no response from mouse or keyboard, even when X was not running.
My system: Ubuntu 10.04 (2.6.32-43 Kernel, 64-bit).

In my case it had nothing t o with the graphics card but with the wireless network card (Atheros based D-link, ath5k driver)
My thanks go to Daniel Ferradal (dferradal) , who first pointed out the possibility of being the wireless card driver.

I unloaded the driver after boot and no more hang. for 3 days.

So for those that have the original bug symptoms (complete freeze, not just X), disable or remove the wireless card and see if it helps.

At least in my case the freeze happens only when the ath5k module is loaded.