I'd guess there's a DNS misconfiguration on the network somewhere - first choice the router/gateway between the subnets.
If you can get a server login, then the IP routing's OK, but the Pub App name needs to be resolved somehow.
Can you ping the MetaFrame server by name from the client? Is the FQDN returned if you use ping -a?
I hope this helps CitrixEngineer@yahoo.co.uk