SOLUTION TO CHASSIS INTRUDED :
I had same problem few days ago.
I tryed everything, clear CMOS every time when PC start, but when I shut down my PC problem was back.
I tryed to update my BIOS, but this was mistake.
I have ASUS P5Q Deluxe mobo and SOLUTION for my was, that I update my BIOS, but no on newest version, but on older version - (P5Q Deluxe BIOS 2201)
So, just try to update your BIOS on older version.
Now everything is ok, no fuc.ing error,...
PS: Sorry for my english.
I hope that this will help you.