Hey folks,

I've been running new vegas for a while (50 hours played) with no issues. Suddenly the following has started to happen:

Randomly at any time during the game, bot in VATS and out, my screen will freeze and small red boxes will emerge in a checkerboard shape. After a few seconds, my whole system reboots as if I hit the reset button.

Any ideas as to what is going on?

Sounds like its possibly the beginning of the end for your graphics card.
I have a gtx280, that exhibited somewhat similar graphic pixallation.
Started randomly while playing FONV., midgame the screen went to crazy pink n purple pixels and I lost total control of pc. But in my case, I was forced to reset the pc manually, opposed to your automatic reset.
According to harwdware forum I reviewed at the time it's caused by "microfractures" on the vid card from the hot to cool temp changes.
My instances were random and sporatic at first and grew more frequent over a short period of time until I wasn't even able to load into the OS without this occurring. Finally had to replace the graphics card. DELL swapped it with a refurb which again its starting to do the same thing only a few months later. (I've learned recently that this is a relatively common problem with the 280 series)

Before assuming the worse however,

You could try the usual trouble shooting steps of updating all drivers, run maintenance utilities etc.
maybe try monitoring your gpu temps while playing to see if there's a spike or pattern to these crashed. Perhaps consider adding heatsink or cooling if this is the case and is occurring primarily during any graphics heavy games.

Good luck

Sounds like a blue screen. CHeck your event viewer for some more info about the error. Windows 7? YOu can type event viewer in the start menu textbox.

If it is a blue screen, you can try to catch it and write down some info about it. Right click on my computer and select properties. CLick advanced system settings on the left and then the setttings button under the startup and recovery label.
Uncheck the auto restart checkbox.

THis can indeed indicate failing hardware. It can also be caused by drivers or conflicting software. If this just occurred out of the blue with no system changes at all then its probably hardware.