Flash sometimes hogs the CPU when I play video with it on Youtube. Roughly half of the time when the player is started, it doesn't use an excessive amount of CPU, however sometimes when the player is started, it will hog the CPU to such an extent that even the mouse cursor lags -- for the duration of the video being played.

My system is 32-bit Slackware 13.1.0 on a fast x86 (Core i7, 4 GHz, 6 GiB RAM, GTX480).
I have tried to upgrade the version of flash on my system.
I have tried to upgrade Firefox.
I have tried to upgrade the NVIDIA graphics drivers.

I have this issue on another fast x86 as well, which is running 64-bit Slackware 13.1.0.

I've had the best luck with the Incubator version of flash, with "OverrideGPUValidation=true" in my /etc/adobe/mms.cfg configuration file.

May I ask why you are running a 32 bit version on this system? With a machine like that I would definitely go for a 64 bit Slackware.

Okay, Flash 11 is out. It's good.

I have the following in /etc/adobe/mms.cfg:

Right-clicking on videos on Youtube gives me: "software video rendering, hardware video decoding." If I use the "full screen" button on the bottom right, then the video does not run at full frame-rate. BUT, if I instead right-click on the video and choose "pop out" to open it in a pop-out window, and then use my window manager's maximize button to maximize it, THEN, the video runs at full frame-rate while filling the screen!

Vimeo videos run fine full-screen. As far as I can tell, they run at the same rate-rate as they do windowed, just with more obvious ghosting.

This is with version 2.75 of the nvidia drivers, on a pure 64-bit system.

EDIT: it has the side effect of very frequently locking up the computer.