Hiya,
What he wdb said ...
also, now when the screen agent just stops and disconnects. Is the screenapp still running i.e screenagent.exe visible in taskmanager? Does the application simply stop running all together?
The fact it works for a moment rules port issues etc...I would be inclined to interrogate the difference between the PC's. Do the logs show anything of interest?
Have you checked with NICE if there is a conflict with any of the software you are using on the PC's? In particular I would check for DVD software, may sound random but it has caused conflict issues in the past.