Internet printing

I installed internet printing in W2k3, enabled ASPs, etc.
I can see the printer and the queue from remote computer, however when I try
to connect I get the message "Printer not found on server, unable to
connect.
It is an older Lexmark Optra 1275 and Windows has its' own drivers for it.
I learned that I have to log in as "my IP\user name" in order to
athenticate, but it still won't work.
It works fine when I try to connect via browser from local network.

Thank you in advance.
Patrick