Re associate the extension with the player.
Dont think its that. The player will launch fine, it will just stop on the blank screen before playing anything.
And if I launch the player and then manually load the file, the same thing will happen. It will stop at the black screen without playing anything.
Have you tried system restore?
Look into getting Acronis True Image. It allows you to back up your OS and create incremental back-ups. They even have a "try before you buy" feature that will allow you to restore your computer to the way it was before you installed trial versions of software.
Thanks for your reply. I spend hours every day making sure a couple of TBs worth of data is backed up both on and offsite, and it didnt even occur to me to just restore my system. I did that, and it did the trick.
Its a shame that Microsoft made codecs etc so difficult to work with, makes loading anything to do with video on your computer like dicing with the devil. And I dont think there is an improvement in Win 7.