Do you have the latest service pack installed, I beleive SP6a for 5.0 is found at:
http://support.novell.com/cgi-bin/search/searchtid.cgi?/2958185.htm.
As well as the 4.83 client?
Have you run dsrepair until clear?
The following is from the 5.1 manual, but should work as well for 5.0:
Using MONITOR to Clear the Connection
Select Available Options > Connections.
A list of active connections appears.
(Optional) To view a workstation's open files, select the workstation's connection.
After viewing files, press Esc to return to the Active Connections list.
Clear one or more connections, as follows:
To clear one connection, highlight the connection and press Delete. At the Clear Connection? prompt, select Yes.
To delete multiple connections, highlight each connection and press F5 to mark it. Then press Delete. At the Clear Connection? prompt, select Yes.
To clear all unused (not logged in) connections, press F6.
Deleted connections are no longer listed onthe Active Connections list.
It would seem the root of your problem is what is causing the lockups?? By shared, I hope you mean they all have the correct NetWare Rights enabled?
Do you run compression on this server, databases should never becompressed! Do you run a Virus Scanner on the Access, this also should be discouraged
Have you considered a network database such as MY SQL or SQL 7 or Oracle?