Subject FB and VPN

My (Delphi) application uses FB embedded (1.56 by default right now; connection via IBObjects) and works great. I have a user who wants to run it over a VPN and it times out on him. He replaced the 1.56 library with 2.5 and installed 2.5 on the server, but this did not fix the problem. 

Any suggestions to getting this to work? We are looking at going to 3.x, but have been overwhelmed with other issues at the moment.

Ed Dressel