WinCC Lockup

I am running 2 Windows 2000 machines in a server/client configuration using WinLC soft PLC using S7 V5.2 and WinCC V5.1. At random times and intervals the Server seems to lose it's connection to the PC, but ONLY the read part of the connection. All of the data goes to zero but tags do not 'grey out'. I can still write to the PLC and start/stop motors etc but with no feedback that I have done so succesfully. The Client still runs perfect and reflects current status with no problems. The server does not re-establish itself but if I 'EndTask' runtime from Taskmanager and open the start screen in Graphics Designer and activate it it resumes and clears the problem.
Banging my head against a wall here so if anyone has any ideas or has seen this before I would be VERY gratefull if you could post them.

Thanks for your time and efforts

Colin