I was posting my Merry Xmas video, so I thought I'd copy n post this from another forum while I was at it...

If you're on an older system, and playback stutters, try these:

1 - Right click in the player window. Uncheck "Enable Hardware Acceleration."

More info here:

Adobe - Flash Player : Help - Display Settings (http://www.macromedia.com/support/documentation/en/flashplayer/help/help01.html)

"For hardware-accelerated scaling to work, you need Microsoft® DirectX 9 with VRAM 128 MB for Windows and OpenGL for Apple® Macintosh®, OS X v10.2 or higher. There might be compatibility issues with older hardware and drivers."

2 - Open a YouTube/Vimeo/whatever page.
Open Windows Task Manager (I bet there's an equivalent for the Mac)
select 'processes'
right click the browser's process (if you have several browser windows open, it's likely to be the one using most memory)
Select priority / AboveNormal
This will stay at that level until you close the process.
This works a treat for other progs too.

Anyone care to add more?

Merry Xmas everyone!