Issues with Windows NT^© versions:
Are you on service pack 6 instead of service pack 6a or another service pack?
If so, expect lots of problems. Microsoft has acknowledged that service pack 6 broke a lot of things network-wise. You can get service pack 6a at their site or you can go back to service pack 5, either of which is stable. In addition, do NOT mix service packs on different NT machines on your network. In other words, run all your NT machines on service pack 5 or on service pack 6a, but not a mix of both service packs.

Windows NT^© OpLock settings:
The file system used in our programs (Topspeed, with extension: .TPS) generates ISAM files. By default, NT4 is set up for SQL files. You need to edit the server's Registry to make it work properly for ISAM files.
NOTE: At this time CompuChem cannot be run on a file server which is running Microsoft SQL server.

WARNING:
The following instructions deal with editing the server's Registry, under no circumstances is this to be done by anyone except your network engineer, even if you are extensively experienced with configuring Windows NT^© it is still desirable that only a qualified network engineer deal with the Registry as any mistakes can have far reaching implications.
We strongly suggest that you ask your network engineer to read through the information on this page as it is of a highly technical nature and will definitely be of assistance to them.

Windows NT^© Clients:
Microsoft has discovered problems in the Windows NT^© 4.0 environment in which the Windows NT^© client can cause database corruption in applications that share files on NT servers.
In addition Opportunistic locks on an NT workstation should be disabled.

The following registry entries are used to enable or disable OpLocks for the Windows NT^© Workstation. These registry keys may not exist by default. To access the registry run 'REGEDT32.EXE' from the File menu, choose Run in Program Manager or File Manager.

WARNING:
Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT^© to correct them. We cannot guarantee that any problems resulting from the use of Microsoft's Registry Editor can be solved. Use this tool at your own risk.

\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters

Turn off Opportunistic Locking by changing the following value to 0.
UseOpportunisticLocking    REG_DWORD
Value: 0 (False)

Windows NT^© Server:
Microsoft has reported problems in the Windows NT^© 4.0 environment in which the Windows NT^© server in combination with incorrect registry setting can cause database corruption in applications that share files on NT servers.

It is critical that you verify that your server has the three settings described below. The first setting listed below already existing in default setting on NT 4.0 server. the second two must be added.

The paragraph below is a description of Opportunistic Locking and RFCB Caching on Windows NT^© Servers:

Windows NT^©, by default, caches file handles to increase performance of some Windows^© applications. This caching causes problems with database applications that use Standard File and Record Locking. In addition, Opportunistic Locking (oplock), which allows each client to cache its own file close requests rather than allowing the application to close its own file handles can also create problems. To disable RFCB Caching and Opportunistic Locking, modifications need to be made to the registry on the Windows NT^© Server as follows:

The following registry entries are used to enable or disable oplocks for Windows NT^© Workstation or Server. These registry keys may not exist by default. To access the registry run 'REGEDT32.EXE' from the File menu, choose Run in Program Manager or File Manager.

WARNING:
Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT^© to correct them. We cannot guarantee that any problems resulting from the use of Microsoft's Registry Editor can be solved. Use this tool at your own risk.

System Registry Workstation Server Service Entries Location:

\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters

EnableOplocks    REG_DWORD
Value: 0 (False)
Specifies whether the server allows clients to use oplocks on files. Oplocks are a significant performance enhancement, but have the potential to cause lost cached data on some networks, particularly wide-area networks.

EnableOpLockForceClose    REG_DWORD
Value: 1 (True)

CachedOpenLimit    REG_DWORD
Value: 0