I got a weird problem here: I have a notebook with a 9700M GT card, and Windows 7 final/Ubuntu 9.10 in Dual-Boot.
Booting Ubuntu works fine, graphics output is good, I got compositing -- using the nVidia binary driver. But if I boot (i.e. "warm reboot") into Win7 right after Ubuntu, the card reports Error 43 in the hardware manager, and Aero gets disabled. Rebooting and starting Win7 again, everything works (i.e. Aero is working fine, glass everywhere, etc.). Shutting the machine down in Ubuntu and starting Windows 7 also works fine, it's just in the "soft reboot" scenario that I have problems.
Any ideas what might be causing this?