I misread the post.
Connecting with tcp/ip is a good idea. If there's a bad file at least it won't break the connection.
It could also be something with Windows Messaging. Or maybe a corrupt tcp/ip stack.
I might try uninstalling the Netware Client, Groupwise and all the networking configurations. Delete the Novell folder from C: Drive and reinstall everything. And while your at it , upgrade to the latest NetWare client - version 4.8.
Good luck! I hope this helps.
Mark