Help!: '02 Impala Radio stuck ON/battery draining

Wife just called to tell me the radio on my '02 Impala (3.4l base model, 70kmiles) won't shut off, and the clock is illuminated but stuck. It's like the dash electronics are latched into a state and won't come out. Of course, the battery will be dead in fairly short order, so I'm going home to disconnect the battery to see if that resets it, but if it doesn't, any ideas???

I got home from work, and sure enough, the radio was blaring inside the car! I quickly tested several other electrical features (windows, locks, air, etc.) and they all seemed to work fine. It was just the radio/clock combo unit - frozen in time. Couldn't shut it off, couldn't turn the volume down, nothing. I tried accessing the menus to possibly reset it that way, but that didn't work either. So, then I pulled the fuse. I didn't realize that this car has TWO fuse panels in the cabin area (one on either end of the dashboard) - actually read the owner's manual and discovered this. Anyway, I had a few other things to do, so right now it's sitting there with no fuse panel cover and no fuse. I'll probably re-insert it on Friday. Don't want to deal with it right now. I DID call the dealer and they said the radio is designed to play with the key removed, but then once the door is opened it's supposed to turn off. He mentioned that the Body Control Module might be the problem. I hope not. "Modules" usually aren't cheap. Anyway, I'll post back when I reinsert the fuse. Hopefully, it's brains will be cleared. If not, I'll probably pull the battery cable to see if THAT does anything. After that, who knows...

One other thing that WAS strange, however: whereas the car normally runs at mid-scale on the temperature guage (~200 deg), now it's running at 1/4 scale (or 170 degrees). I doubt this is true.