A frequent cause of this on Windows Vista and 7 is not having the "Aero" feature of Windows enabled. Your graphics card and graphics memory must have a certain performance level, but it's easy to find out if you can turn it on.
Just follow these instructions:
1) Click Start-> Control Panel
2) In the Search bar at the top right, type in "aero"
3) Under the Troubleshooting header, click "Find and fix problems with transparency and other visual effects"
4) Click Next, and the graphics test will run.
If your system can handle Aero, it will automatically be turned on! This will greatly help with the performance of the Youtorial Player.