Just to piggyback on Frank's response:
Can they open the .prn file in notepad. It's just plain text, so if they can't
open it there, then it may have been corrupted in the ether!
If it looks ok in Notepad, how do they try to open it in excel--ask them to use
File|open. They should see the text to columns wizard appear.
If you continue having trouble sending/receiving the .prn file, you may want to
try to zip it (
www.winzip.com has an evaluation version).
They may have better luck -- or maybe the zip file will arrive corrupted (if
you're really unlucky!).