Problem with Flash on Youtube

Hi everybody,

i'm italian, so sorry for my bad english.

My system is Windows 7 64bit. Browser Firefox 10.1 , Flash Player plug in 11.1.102.62

I have a hard question.

Look at this pics:

https://docs.google.com/file/d/0BzXyQEhp-88lODc1Y2Q3NGItN2FmMy00MGZjLT gzYmYtNjdlNTliYTFkZDhj/edit

How you can see, when i activate flash plug in the youtube bar (and the video) looks... "pixeled" (or zoomed??)... (pic on top)

but when i deactivate flash plug-in the bar and video look good (pic on bottom). So i can watch video with HTML5.

I could not solve this problem in any way. I disabled the option "hardware acceleration" but it did not do anything.

The problem occurs even when using different browsers like Google Chrome and Internet Explorer. I have updated all drivers on my computer,

even the operating system. But it did not solve anything!

I updated my graphic card with newest drivers (HD Radeon 6770M) but it did not solve anything!

If I watch a video on Vimeo I can see them well. So the problem is only on youtube.

How can I fix it?

please help me