From what I understand, all of my browsers are up-to-date and should work fine with WebGL. For instance:

Google Chrome: 13.0.782.107
Chromium: 15.0.847.0 (Developer Build 95927 Mac OS X)
Firefox: 5.0.1

So I'm thinking it's my video card. My MacBook is from the summer of 2007 (getting "old"), with an ATI Radeon X1600:

Code :
Model Name:	MacBook Pro
Model Identifier:	MacBookPro2,2
Processor Name:	Intel Core 2 Duo
Processor Speed:	2.33 GHz
Number Of Processors:	1
Total Number Of Cores:	2
L2 Cache:	4 MB
Memory:	2 GB
Bus Speed:	667 MHz
 
ATI Radeon X1600:
 
  Chipset Model:	ATY,RadeonX1600
  Type:	GPU
  Bus:	PCIe
  PCIe Lane Width:	x16
  VRAM (Total):	256 MB
  Vendor:	ATI (0x1002)
  Device ID:	0x71c5
  Revision ID:	0x0000
  ROM Revision:	113-xxxxxx-158
  EFI Driver Version:	01.00.158

It seems like once I updated from Leopard to Snow Leopard recently, WebGL stopped working on my machine. I've tried "Software Update" multiple times but haven't been prompted to download a new video driver. And I don't know any other way to update the video drivers for a Mac.

Thoughts?