Mr. Kill,
I have seen two computers with error messages appearing when AH is shut down, and only a reboot will solve the problem. Both use Athlon chips.
On the first, I discovered the problem popped up when I changed the video driver. I uninstalled Aces High, reinstalled it, and the problem went away. An uninstall and reinstall is worth a try if you have changed DirectX or a video driver.
On the second machine, I tried all of these fixes, and it still hasn't fixed the problem. That machine has some type of Athlon MB and chip, but I cannot be specific.