System lock-ups and failures (Netware 4.

We have just migrated from a Netware 4.11 network to NT 4.0. We have been experiencing client side (Win95/98) lock-ups when our users try to access their shares. Specifically, these lock-ups occurr when the user is trying to access them through Office97/98 apps – Word, Excel, Outlook, etc. After rebooting they are able to reconnect but invariably lock-up again. Any recommendations or suggestions?