This is very similar to a question answered here recently (
http://www.experts-exchange.com/Networking/Novell_Netware/Q_25340131.html)From that question:
Timeouts can happen as the NetWare client tries to resolve the windows server name in the UNC, so the client needs to be told which servers to *not* try to resolve.. You need to go into advanced setting in the client, and reduce the bad server timeouts to 1 or 2 seconds, and make sure the bad server cache in enabled, Then add a registry entry as per this TID:
http://support.novell.com/docs/Tids/Solutions/10090785.html
We did that with our hybrid network, and there are no slow downs accessing the windows servers.