Sometimes, you get the bear. Sometimes, the bear gets you.
I was looking for decoder deals on our favorite auction site when I ran across a sale of an Atlas U25B, not running, for less than the price of a standard decoder. I thought, if nothing else I can use the thing for parts, so I bought it. This evening it arrived in the mail. The box says it's factory DCC equipped, so maybe the decoder is bad, or isn't making good electrical contact. I put it on the track, and sure enough--nothing.
I stuck it on the programming track, and found it had been assigned a completely random address (10), and had analog turned off. So, if somebody put it on the track, it wouldn't have done anything on straight DC, and nobody would have guessed that engine 6609 was assigned address 10. I assigned it the cab number as the address, put it on the track, and away it went. It's currently tooling around the layout as I type.
Looks like this time, I got the bear...