What's the version shown in the help-about box of boinc manager?

The manager is not really needed to compute 'in the background'. Just exit the manager via the file menu option. Unless previously the box to also close the agent was ticked on manager exit, boinc will continue, no icon showing the the system tray. Relaunch the manager as and when you need.

Cause: Probably something in the drivers of the display. You could try with updating them, though some installations do not allow this or break a lot. Make a backup before doing so.