I've had the same problem and it is still unresolved. Citrix' site and this forum suggest installing printers unknown to NT Term Svr on the server, which I did. Unfortunately, my users are still unable to print. My next step is to setup a testbed at our main office with a 3100 and rule out any operator issues, but that's probably relegated to next week.
I'll report on how it goes when I am able to do it. I haven't yet contacted Citrix by phone, I'm going to see how the testbed works first.