On my laptop with a Mobility Radeon M7 on I noticed the same problem after a kernel recompilation (2.6 series ~x86 flag); that is I had Direct Rendering switched off. I was compiling AGP as a kernel module. Actually I solved the problem compiling AGP directly in the kernel with the chipset code too. I'm also using x11-drm to obtain the correct Radeon driver compiled as a module.
I made an attempt to use ati-drivers package but I found that it doesn't complain my card anymore. -- gentoo-user@gentoo.org mailing list
