Ok, I've been getting a similar error from my WMP v9.0. I'm running windows 2000 Sp4. The problem started after I installed the latest Divx codec pack, 5.2.1, not 100% sure of that version #. I have since uninstalled the codec pack and re-installed a codec pack from Microsoft, but the problem persists. The thing is, I get the error if I left click a media file, be it mpg or anything else, and try to run it from the web page. If I right click and save as, and run it from my desktop no problem. I get the Error message and it also has a box checked that says "Restart Windows Media player"