White flashing on embedded video on MP?

[Feek]

Over the last couple of weeks I've noticed that any embedded video I play from youtube or pretty much any web site has a load of white flashes through it. This is in both Firefox and Safari.

Has anyone experienced this? I'm sure it only started recently.

Mac Pro, 8800 graphics card, 10.5.6 all patched.

 

[Feek]

Well, I restarted and it's OK now. Odd. I don't do that very often, I just normally sleep the Mac when I go to work or bed.