Use a pop list. As I recall scripts never really work good with drop down lists
Never mind . . .
This was one of those times where I made an bad assumption that had me looking in the wrong place. The problem wasn't with the script trigger, but with the value lists. I think I know what I did wrong, though I'm not sure why it seemed to work before. Anyway, it all works now.
Thanks for the advice, though. . .