I had this problem too, with the A7N266-C. I was able to work around it by forcing the APM Daemon to not load (by removing the ???apmd files in the /etc/rc.d/rc.# directories).
But then X would continually crash after login, since both Gnome and KDE load their own APM Daemons. So, I finally downloaded Fluxbox and that worked.
Anyway, I never was able to find a solution on my A7N266-C motherboard, but it was finally fixed when I upgraded to an A7N8X. As a side note, I think Asus did a crappy job on the A7N266-C.
"Physics is like sex. Sure, it may give some practical results, but that's not why we do it." - Richard P. Feynman