360 video issue

I have one of the original 360 premiums and have been more than happy with it. Everything has been working fine until today. After leaving my 360 untouched for a week, I decided to go get some Fable 2 time in while my girlfriend is out doing errands. When I boot up the system, it tells me there's an update waiting to be installed. I let it do its thing, and once the install is finished, I boot up Fable 2. The game lasts for all of a minute, then will do any of the following: screen suddenly becomes wavy snow, screen suddenly goes black, screen suddenly goes to a very dark blocky texture reminiscent of an aging NES struggling to output video, and so on. I've tried a few different things, both in game and just in the dashboard, and the loss of video always happens. While video is out, the 360 doesn't show any unusual, ominous red rings.

So what are my options? My first thought is that the update has managed to brick my 360, but I have no idea how I can roll back updates, especially since I don't get a lot of screen time before the machine asplodes. Is there anything I can try, or am I destined to have a rousing discussion with my friendly neighborhood MS CSR?

UPDATE: After following some of Microsoft's online troubleshooting suggestions, I have booted up my 360 to a wonderful trio of flashing red lights. I guess that answers all my questions.

UPDATE: Not content to let the Ring of Light to dictate my fate, I continued to fiddle. I removed my wireless adapter and the hard drive and booted up. I managed to get to my dashboard with no problems. Hooray, I think! I reattached the HD, booted up again, and got another screen freeze. After a few tries, I managed to wrestle my way to system settings and cleared the cache. After that, I play the RE 5 demo without any problems, so... maybe I fixed it? Maybe the 360 is biding its time, waiting to lull me into a false sense security before striking the final crushing blow? We'll see. Back to Fable 2, hopefully without any problems from hereon out.

It's only a matter of time until it explodes.