"Can't open display" problems

[Trevor Wood <twood@bu.edu>]

I just upgraded from potato to woody and found that I cannot open my
display for X apps anymore.  My hostname is MEDESIGN, so I used to set my
DISPLAY environment variable to MEDESIGN:0.  Now I have to set it to :0.0
to run local X apps.  

However, this won't work when I try to run an X application from a remote
ssh connection.  

This sounds like an embarrassingly stupid problem, but how do I fix it?

Thanks in advance,

Trevor