In Windows 7 (I'm using Enterprise), some DirectX applications (For example VLC media player) do not show a proper full-screen preview when I move my mouse over the mini preview in the taskbar. The image stays stuck at a specific frame, and occassionally updates, sometimes only updating part of the image. The mini preview, however, updates fine with proper frame-rate. I noticed that this doesn't happen with Windows Media Player, but all other DirectX apps I tried have this problem.
Is this a known issue? Since it happens with multiple applications it doesn't seem like its the applications fault. I'm guessing that Microsoft added special logic for WMP to make it work. I also tried on several different machines, same issue.