Remote Desktop Refusing to Work

It worked for a while...but not it has stopped all
together. Here's my scenario.

My intention was to set it up to work over a dial up
connection, so that the remote user, (Who lives out in
the boonies...where no high speed internet exists) can
dial in and use remote desktop. Using the dial up
networking feature, and then by typing in the computer's
name, it actually worked for a while. It did from my
laptop I brought to the office to test it on...and it did
on my computer at home.

And...now, it just plain doesn't. I can dial in, (Can't
file share...which is a whole other problem altogether)
but when I try to use Remote Desktop, I get the
message "Specified computer cannot be found. Check IP
and name etc. etc." It doesn't even work on the
computers hardwired to it by LAN. I'm not quite sure I
know what I'm doing. Any help?

- Mark