My office runs a Citrix farm. Of course, they do not support Macs. My Citrix admin is a Mac user and has been trying to help, but I was still stuck. I run Panther and the Citrix client default connection type is TCP/HTTP. This gives a "Cannot locate server" error, even though I have good DNS.
I played around with the connection type and changed it to just TCP, and bam, it worked. I now can run Citirx client on Panther without running Virtual PC. Cool!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030925152808510