I have 6 sata drives 2 use raid port has worked fine for the last 3 months.
Untill I got bios hang at post .
stopped at ACPI controler
Asus A8n SLI Deluxe
4 gig memory
6 sata drives
1 IDE drive: boot
gt7900 oc pci e
Check the cables sounds like the BIOS is having trouble getting data on something. If everything seems fine, then I say first disconnect all the hard drives to see if it posts and enters the BIOS. If that works, try it with first the boot drive, then try to post with the other drivers, and of course try the RAID array last. If it doesn't work when you disconnect all the drives it could be the board dying from old age ^_^.