Flash Player Square troubles in Mac OS X Snow Leopard

For the last 2 - 3 days or so, I have been having severe problems with Flash Player Square Preview 2, 64-bit in Firefox 4.0 Beta 7.

Most sites seem to work fine, but on YouTube nearly every video I try to play performs very poorly. The video lags horribly, and is very choppy and blocky.

I have tried the following:

1. Uninstalling/Reinstalling Flash Player - No Success.

2. Deleted my Firefox profile. - No Success

3. Playing videos with fresh profile and NO ADDONS. - No Success.

and Finally,

4. Reinstalled Mac OS X Snow Leopard 10.6.5 - No Success.

Also one more important thing to note, I had a friend with a similar setup(Firefox 4.0 Beta 7 - Mac OS X Snow Leopard 10.6.5) as my own try it, and he too said that the videos are playing choppily with the same results.

Flash does however, perform well on every site in 32-bit release versions of Firefox 3.6.X as well as Safari and Chrome. And it performed fine even in a 64-bit Browser earlier this week too.

Also, I do not believe the problem is 64-bit related, since I get the same results if I tick the Open in 32-bit Mode check box in Get Info for Firefox 4.0 Beta 7.

Any suggestions for this problem would be much appreciated.