Random shutdown w/ unsuccessful reboot

While I see there are plenty of Random Restart threads already, I haven't found one with my exact case and have yet to find any answers.

My system randomly tries to restart, always when idle, and usually in the middle of the night. Because of this, I'm not sure if a BSOD is occurring, which I've only witnessed once since upgrading to Win7.

I will wake up to find my computer frozen on the black "Starting Windows" screen, where only the text is visible, without the animated windows logo above. I restart, and Windows starts to go through its repair diagnosis, which has never found an issue and I usually just cancel (I cannot select "start windows normally" before this since my bluetooth keyboard isn't registering keystrokes at this point). This restarts my computer again, and this time I get past the black "Starting Windows" screen. The blue startup screen starts to configure updates, fails, reverts changes, and restarts once more. This time my system boots up normally.

This used to be an occasional occurrence (but without the update attempt and extra restart), and now happens every night. Every Win7 update attempt has failed in this way since 1/28.

I have Windows 7 32-bit, upgraded from XP
Intel Q6600 2.4ghz
4gb ram
ATI Radeon HD 4650 1gb

Any help would be GREATLY appreciated. Thanks

I'm sorry Jonathan but what steps are those? The link seems to be unrelated. Do I simply zip my files in Windows/minidump and attach it here?

And yes, my time is set to sync with the windows time server.

Here you go. Thanks for the help.