It's not a black screen for me, the flash video area just disappears and becomes transparent, so say I have MS word open underneath a chrome window @ youtube.com, the video area would be see through and you'd see the MS word document underneath.
It's really strange, also I'm not using any extensions
EDIT: did some Googling, turns out there was an update recently to 7.517.44 and it came with a newer version of flash, it was released ~Nov 4th, so this could just be a version of flash that doesn't get along with my laptop. Bummer, looks like I'll be waiting for the next stable release...or jump onto Beta