With a PVR250/350, yes GBPVR or WinTV or any other TV app could be causing the problem. These very early devices only allowed one application to construct a directshow graph at a time. All later devices allow multiple application to have a graph constructed at the same time, but only allowed one graph to run at a time.
The exceptions seem to have stopped after another reinstall.
As an experiment, I have set up recordings every night for 1/2 hour every hour on the 1/2 hour. When my EPG update was at 2AM the 2:30 recording was OK but the 3:30 and beyond failed. Last night I moved the EPG update to 1:00. Now the 1:30 recording was OK and the 2:30 failed. I would have expected a problem immediately after the update not 1 recording later.
Looks like the problem was caused by Microsoft Media Center. I uninstalled it and everything was fine last night. Now just the unhandled exceptions when deleting video files.