Navision 3.60A SQL 2000 performance

We have Navision 3.60A with a SQL Server 2000 database. We are facing frequent instances of users being blocked, slowing most of the clients down. Specially when someone is running the MPS, the user blocks other users who are trying to post shipments etc. Is this a known issue? Is there a fix for this? Or is there a tool to overcome this? Thanks in Advance