I _believe_ homeworld 2 doesn't recognize FireGL drivers or Quadro drivers properly.
Do you still get the black-boxes with the updated drivers??? (I know you said you got the error, but ignore that error).
Last resort, you can use CATALYST drivers on your notebook that should not give you the error (but they are not workstation-app certified, and as such, won't perform nearly as nice with autoCAD, 3dmax, Maya, etc.
You can always revert back...but anyways...
Try with the latest FireGL drivers you downloaded. If no success and you want to try CATALYST drivers...
Download drivers from www.atitech.com
for the DESKTOP Radeon 9000 series for your operating system.
Then go to www.driverheaven.net
and download the Mobility Modder tool (made by Pajet).
Modify and install the drivers (The mobility modder works for the FireGL mobility 9000), and then give the game a go.
Should do the trick.