The problem with the UFO is indeed shorting. The one that came with my clamshell started shorting around the connector. After a while, it no longer would work without jiggling it a bit, and eventually it died altogether. I'm using a third party one right now and have been for five years but am looking for a replacement Apple one simply because the third party device doesn't appear to charge the battery--I used to always blame this on the batteries being without any charge for two weeks, but now I'm thinking it's simply the adapter not being a charger--a similar thing happened to my cousin, whose iBook G4 would no longer charge once she got a third party adapter but suddenly started charging again when she got an Apple.

I think I'll be looking for a non-UFO and would advise anyone else to do the same.