Firefox locking with YouTube

[Bart Silverstrim]

Has anyone been seeing this behavior recently, or know how to try 
troubleshooting it?

When I go to Youtube.com and click a video to play, Firefox starts 
rendering the webpage, and when it starts retrieving the video link to 
play it FF dims and "locks up", and I have to force quit Firefox.  I can 
still minimize it and move the window around and use other applications 
but FF is dead until I relaunch it (and don't restore the session to 
play the video, unless I quickly close the offending tab before it has a 
chance to try bringing up the video link).

Could a recent update have caused this, and is anyone else seeing this 
issue?

-Bart