Error Code -50 when connecting to AFP share

For some reason, I cannot connect to a certain AFP server over the Internet from one of my macs at home. I have two macs, and the other one connects to it just fine. I’ve even tried reinstalling Tiger to see if that fixes it, but it doesn’t. Since from the same location one computer will connect but the other one won’t, could it have something to do with the network card?

What happens is, I can connect to the AFP server with the user name and password, and it lets me select the available shares to mount, but when I try to mount any of them, I get this:

“Sorry, the operation could not be completed because an unexpected error occurred. (Error Code -50).”

Anyone come across this before?

Thanks