Well, it looks like it's the sensor that went bad. I got out my backup player and upgraded it to 2.0b11 and then connected the two players to hyperterm and did the self test...

My original player:

0400 temperature detect
0410 temperature is 00
04f0 temperature ok

My backup:

0400 temperature detect
0410 temperature is 31
04f0 temperature ok


This bites. It's going to bug me now that I know one of my players isn't functioning right.