I had this problem too. I eventually traced it to an incompatibility with the Realplayer 14.0.2 extension. When I disabled the Realplayer extnsion WMV files played normally.

I upgraded Realplayer to the latest version, which updated my Realplayer extension to 14.0.3 which resolved the problem and I can now play WMV files normally with Realplayer enabled too.

Best wishes

Mike H

Thanks. I've already downgraded back to Firefox 3.6.17 and everything works fine, but I'll try your solution if I decide to go back to version 4. I wish Mozilla had taken the time to work this out prior to releasing version 4 and leaving us to solve these problems for ourselves.

All the best, RL

I converted the files to .mov extensions and now it works fine. I have not tested this on a pc but will have the results by the end of the week. Will let you know.

For me official wmv plugin works properly on that page. Check in your installation folder subfolder 'plugins' and there NPMSWMP.dll.