opengl - Why do I have low FPS unless root?

Problem:
Normal users aren't using the best graphics driver. I first noticed this playing Osmos from the HumbleBundle2, but I can observe it while running glxgears too. Maximised on a 1280x1024, glxgears averages a choppy 60 frames in 5 seconds, vs a smooth 300 frames every 5 seconds for root.

Here's some glxinfo:

jake@daedalus:~$ glxinfo | grep "renderer string"

OpenGL renderer string: Software Rasterizer
jake@daedalus:~$ sudo glxinfo | grep "renderer string"
[sudo] password for jake: 
OpenGL renderer string: Mesa DRI R300 (RV380 5B60) 20090101 x86/MMX+/3DNow!+/SSE2 TCL DRI2

I have the same problem even after rebooting (powering down, cycling surge protector). I followed the directions at the Ubuntu wiki for getting rid of fglrx, but no dice. What else can I do?

Hardware:
Radeon x300

AMD Athlon 1.8 GHz
1.5 GB ram

I wonder if adding yourself to the 'video' group (I think) would help?

sudo adduser $USERNAME video

Can someone confirm the group name? Thx