taskbar intrusion when using pps

I'm having trouble showing videos in MediaLab. As an alternative I tried showing the videos in a powerpoint show. This worked, but when I run an experiment containing a pps file, a small portion of a blue taskbar randomly becomes visible in the top right-hand corner of the screen for a few seconds at a time, sometimes during the pp show, but also at random times during other questionnaire items. I hav clicked off all of the view options in the pp tools menu as recommended in MediaLab help, but that didn't fix it. Can you tell me how to fix this problem?

What do you see on the task bar? Can you get the task bar to pop up in PowerPoint if you run the show on its own--i.e., independently of MediaLab?