Go to about:config , what are the values for the webgl.disabled and webgl.force-enabled?

If webgl.disabled is true set this to false. If that doesn't help you could try forcing it to be enabled.

Also, do you have the most up to date graphics drivers? This could be another thing to consider.

webgl.disabled is false by default. I switched the force-enabled on but it dodn't make any noticeable difference.

I should have mentioned I'm using the nouveau driver. I get slightly better performance with the proprietary nvidia driver. In my experience most games will either work about as well with nouveau or not at all.

Seems to perhaps be a problem with WebGL and that particular driver perhaps, someone has a similar problem on this page: http://www.reddit.com/r/gamedev/comments/mk7sf/creating_pseu...

Nouveau looks like a cool project, it's probably worth raising it with them as WebGL is going to be important in the future.

I'm using nouveau and Firefox 9.0.1, and I get >30 FPS.

GT218 [NVS 3100M] xorg-x11-drv-nouveau-0.0.16-27.20110720gitb806e3f.fc16.x86_64

you should run glxgears to see what your fps is. it would also tell you if you're using software rendering or not.

GLX gears is a pretty unreliable benchmark: I've gotten anywhere from 300 to 600 FPS on this machine at different times. I usually get around 90 FPS when playing fairly recent games like Modern Warfare 2 (on windows). Perhaps you meant glxinfo, which reports whether direct rendering is enabled (and it is).