Google Product Forums
Re: Video not displaying (black, green, white box) but hear audio? Look here...
razdraz Feb 17, 2011 5:55 PM
Posted in group: YouTube
1) all videos are a black box, no audio, no time scrollbar - nothing in the window except a black box. cookes & cache reset, blocking software off.
2) Mac OS 10.6.6
3) Safari 5.0.3
4) built in Intel GMA X3100
5) 10.2.153.26

(I have the exact problem as abcder...)
FIXFIXFIXIT?

I'd like to also state that I'm rather disgruntled because this forum (http://www.google.com/support/forum/p/youtube/thread?tid=11f8d2154e6f6712&hl=en) was closed without any significant mentioning of a solution to those of us who can't hear any audio!