Ignore this if I have been dreaming, but I would swear there were some bug reports last week about MB suddenly freezing, without crash report. But I can't find them right now.
Today I experienced such a freeze. (v 3.0.5920)
I was playing an 8 second wav file, and I believe MB froze at the moment I pressed 'previous'.
MB stopped and froze completely. It could not be closed with the close button in the right hand top corner.
edit,
And for those wondering, no it was not some obscure wav from a voice machine ;-)
It was a professional file coming from ProTools, so I would not suspect it as being the cuplrit in this case.