Walrus, I just had a similar problem. In fact, if I didn't know better, I'd have thought I made your post. We had some brownouts, and I figured something was fried. I checked the fuse, and it was still intact.

I had unplugged and replugged the unit, and messed with the buttons, but nothing. I left it unplugged, and checked again the next day -- the yellow led lighted up, but went off as soon as I touched something. I fiddled with switches and buttons, but again, nothing worked.

At this point I assumed it was time for repair, but I had left it unplugged for a couple of days. I started to disconnect a couple of the cables, in preparation for sending it back, stopped, and decided to fool with it again. This time, after turning on and mashing buttons, it came back! Works good as new.

So, I guess my advice is to leave it unplugged and off for a couple of days, and see if you can bring it back to life. If not, try sending it in for repair.

The only thing I can figure is that it had to reset its internal memory but aside from that, I dunno!