Have you changed the associated application that you use to play the file? This may explain what it has changed recently.
AFAIK, you now need to delve in to the registry to change icons for file types. However, this GUI appears to be able to do this for you (and is free). I don't know if it will work, but it's worth a shot:
http://www.nirsoft.net/utils/file_types_manager.html
I personally haven't, that's not to say something has changed it with out my knowledge. Right now the option to open with is Windows Media Player. Then in the other programs the choices are as follows: 7z462, IE, MS offiice word, MS works word processor, Paint, windows live photo gallery, windows photo viewer, adobe reader 9.3, MS office picture manager, MS works spreadsheet, notepad, windows live movie maker, windows media center, word pad. Am I missing some other options to open it with.