Comment 13 for bug 1033263

Nvidia just released new drivers.
http://www.nvidia.co.uk/object/linux-display-amd64-304.43-driver-uk.html

Some of the bug fix descriptions look like a solution for the problems I have (playing youtube videos, or just starting firefox caused problems on my machine/ hangs). Just don't know how to (easily) install these drivers to test them:

Fixed a bug that caused pre-release versions of X.Org xserver 1.13 to crash when certain GLX operations were performed, such as when starting Firefox.
Fixed a bug that caused VDPAU to hang when expanding the YouTube Flash Player.
Fixed a bug that caused gnome-settings-daemon to revert display configuration changes made by nvidia-settings.
Updated nvidia-settings to use RandR per-CRTC gamma control, when available. When controlling an X server with support for RandR 1.2, nvidia-settings will display the color correction widget as a tab within each display device page, instead of a per-X screen color correction page.
Fixed a bug that prevented the display palette from being updated immediately after an application called XStoreColors.
Added the ability to select and move X screens in the "X Server Display Configuration" page of nvidia-settings via Ctrl-(Left)Click + Drag.