So, it turns out that this was a problem only in uxterm, not in other
programs like Iceweasel, so I was wrong to blame X. I had tested the key
in Iceweasel, and wasn't able to access the menu bar shortcuts, but
apparently that was just a focus problem and not a key problem.
For now I've just switched to rxvt-unicode and the Alt key behaves as
expected. I found a number of places that have described how to fix what
the problem probably is in xterm, but it doesn't seem worth the trouble
right now.
I'd prefer to just use gnome-terminal, but that isn't installing in
Debian mipsel right now.
--
-John Sullivan
-http://wjsullivan.net
-GPG Key: AE8600B6