The Amp Quits Agin -- Am I Missing Something?

I have a 4b-ST I left on for about 4 hours Friday night only to return to find that one of the channels had died in my absence. While I was gone, the system was on, but not being used. I haven't really investigated at all to guess what may be wrong, other than to determine that that CD player and the preamp are still working fine. The left channel on the Bryston seems to be working fine, as does my left speaker. The right channel, however, appears to be completely dead (even the left LED is dead) and I have no idea what may or may not have happened to my left speaker. I'd love to not have to send the amp back to the shop (again, it was there in February for a muting switch) and am hoping that I might have missed something obvious. Any thouhgts? Thanks.