I have a ASUS p5w-dh board with Intel-SATA-Controllers on it, which I use with AHCI. The mainboard features a raidcontroller, which is apparently wired to ata port 2 and confuses linux while booting. this thread describes the problem: http://www.uwsg.iu.edu/hypermail/linux/kernel/0702.1/0896.html The issue is still there with 2.6.23.
*** This bug has been marked as a duplicate of bug 8923 ***