Hey,
So some of our users had a problem with our player, which in result, they saw a black screen but the sound was working.
I managed to figure why it's happening on the latest version of JW (Trunk, 4.6.248) and all versions that are > 3.
Problem: Flash player update (from adobe) has fucked it up.
Solution: Download flash player version <= 10.22.87.
I've setted up a link for 10.22.87 (http://bit.ly/4hUlGJ) and it solved all our users problems.
Hope it help, and please, fix this on next release!

Are you kidding me? That's your solution?