Are you using any blocking programs/add-ons?

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

I tried starting in safe mode, I disabled Adblocker Ultimate, and I even paused protection in Kaspersky for 1 minute, then started Firefox and still no video.

MSN started putting little pop-up type previews of different articles on the right when I was reading other articles and they were irritating, so I used "block element" in AdBlocker to stop those, but they are still blocked even with AdBlocker disabled and I can't figure out how to unblock those pop-up previews.

I also did some trick typing "about" something into the address bar to stop the audio pop-up from irritating me on download.com and I can't figure out how to undo that, but I don't think either one of those should affect videos on MSN.

I'm at a loss.

I hated doing it, 'cause it's a PITA (not as bad as it used to be), but I finally refreshed Firefox. Problem solved.

I apologize for taking up your time and thank you for responding.

Not a problem. While the root cause of the problem is not known, still, you have your browser back.

Well done, safe surfing.