Same problem here. I talked with someone (while off duty) at my carrier (VZW) and they are stumped.
Mine worked as recently as 5/2/10, but has not worked since. I have not tried the Bolt browser, but both Opera Mini and the standard Blackberry browser do not launch the video like it did a few weeks ago. I too can access youtube via m.youtube.com, but when I click on play video, nothing happens.