Programmer - MediaElement plays video, but no video shows

Programmer Question

I can open a video, play it and get position and set position, but nothing shows up in the video window on one pc. Below is the code of a sample app:

This works fine a on a couple of PCs, but doesn't work on another. Does any one know or can refer me to what files I need to properly run MediaElement on XP pro.

Thanks,
Rob