Just throwing an FYI out there:
I had 2 computers recently that after a reboot/restart just sat on a blank screen before loading Windows 7.
The issue, as it turns out, was that the boot sequence had been changed to USB first, but without any sort of memory device in a USB port, it would hang.
I assume this was some sort of Win7 update "feature." I've got MSE on both machines, and the desktop was just build recently, so I don't think it was something malicious, although it's possible.
As a side note, it doesn't help that I apparently lost power during an update process (and I also started playing with OC Genie and Core Unlock, not realizing how messed up the machine was). So it was a tense hour or so while I repaired Windows and reset the BIOS. In the end, everything looks fine, but I apparently lost Aero (and custom bars/windows) on my custom themes. Weird.