Without going into all the problems people are having utilizing
MS Silverlight 1 or 2b with FF3, here is my recommendation for
you baseball fans (me included) that have MLB.TV or MLB.TV
Premium and don't want to revert back to FF2.

Your choices:

If you have MLB.TV Premium use Mosaic or
If you have MLB.TV or MLB.TV Premium install the FF3 addon
MediaPlayerConnectivity 0.9.1 after uninstalling Silverlight.

MPC 0.9.1 allows embedded media files to play in an external
window rather then an FF window or tab. I have found that MLB.TV
feeds play extraordinarily well using this method. I'm not sure
I'd even go back to Silverlight.