Duncanma said:
pdev, I'm running FF 3.0.1 right now and full screen works for me...  does full screen work for you on other Silverlight players?

http://silverlight.net/learn/learnvideo.aspx?video=76039 is one example if you have a chance to check it out.
Ah, fair question.  So I ran a test, and nope silverlight.net's player didn't work either.  Sorry guys, I guess my problem is elsewhere.