Bug with Full Screen Videos in Safari

Running current version of Safari for mac, full screen videos look like this. It's like this on all videos.

@fantasgasmic: Is this with Safari 6.0.3? Somethig changed with that version which we are trying to track down. Weird cause its fixed in the webkit nightly builds so wondering if a fix is forthcoming in Safari itself.

It appears to be 5.1.7. I am not on Mountain Lion, so it's possible I was left out of 6.0 and didn't know it.