Just sharing what I added to get Gmail voice & video chat working on Firefox (as of 3.6.x):

# Gmail voice & video
/opt/google/talkplugin/** rm,
/opt/google/talkplugin/GoogleTalkPlugin Uxr,
/dev/nvidiactl rw,
/dev/nvidia0 rw,
/dev/zero m,
/proc/interrupts r,

Maybe slightly different if you have an ATI/AMD video card.

I'm not quite sure why the plugin needs to access "/dev/zero" and "/proc/interrupts". Can someone enlighten me?