KB Article: http://support.microsoft.com/kb/939206
Consider the following scenario:
- You are using a Windows Vista-based computer.
- You have Aero Glass disabled, or the video card does not support this mode.
- You are playing a video in Microsoft Windows Media Player.
- You are playing the video in full-screen mode.
- You right-click the full-screen video to display a shortcut menu.
In this scenario, the video playback window becomes unresponsive. If you press CTL+ALT+DEL to exit full-screen mode, Windows Media Player functionality returns.