I have experienced system slow downs when screen agent has been rolled out using a ghost image however never to the point of freezing the workstation or causing it too reboot.

If you've performed a rollout try uninstalling screen agent manually using the clean.bat application and then re-install manually and see if the same thing happens.

What version screen agent are you using? Best way to check this at the top of the screen agent log file.

We are using 8.80.05.10_HF.  We used BartPE/Ghost8 to build/deploy the images which includes the NICE ScreenAgent.  We have uninstalled several workstations and reinstalled.  That all happen this morning so the jury is still out.

Screen agent does not work well with ghost images.  There are registry values where the permissions are changed instead of new values created, apparently ghost images do not pick these changes up.  

It is very rarely I have had customers build ghost images that work well, I always stress heavily that the use the command prompt type installation for rollout operations.