I had a similiar problem with an ATI AIW 8500dv. I ended up upgrading
to xfree86 4.2 from 4.1, (which necessitated an upgrade from "Woody" to
"Testing") this fixed the problem, I specified the radeon driver.
Here is a link to the ATI website where they provide instructions on how
to install a binary module in the kernel to support the 9000.
http://mirror.ati.com/support/drivers/linux/radeon-linux.html
This however involves an rpm package - the process looked to fraught
with danger to me so I chose to upgrade to Xfree86 4.2 instead.
Xfree86 4.3 will contain better support for accelerated 3D, but if all
you need is 2d Xfree86 4.2 will work fine.
Paul Winkler