It should be related to video overlay functions working only on the primary display.
Check if the following applies to your gfx card too, I cannot test it at the moment. I had a problem related to overlay too, but this was on my primary display: I couldn't capture screen. All I did was turn off Windows Media Player hardware acceleration to solve my problem (btw, I have an ATI Radeon). Check if clone display mode works, too. Be sure to write down or remember changes you apply in case you want to roll back to the previous state.
Certain video files which use video overlay may not display properly on a secondary monitor when running in dual monitor mode . To enable video playback on your secondary monitor or TV, Full Screen Video should be enabled. Please follow the directions below to enable Full Screen Video:
1) Right-click on your Desktop and select "Properties."
2) This will bring up the Display Properties control panel. Click on the "Settings" tab and then click on the advanced button.
3) Click on the tab corresponding to the graphics card installed in your computer. For example, if you are using an NVIDIA based GeforceFX 5700 graphics card, choose the GeforceFX 5700 tab. A pull out window will appear to the left of the panel. Select "Full Screen Video" from the left pull out window.
4) The "Full Screen Video" panel will appear. If you are running in Dualview mode, select "Auto-Select" from the "Full Screen Device" drop down menu . If you are running in Clone mode, choose "Secondary Display" from the "Full Screen Device" drop down menu option,
Click the OK button to confirm these changes. When a video, which uses video overlay, is running, the video will now appear in Full Screen mode on your secondary display.