Where abouts is your operating system? Is it on your RAID drive? If so your PC will not boot if your BIOS settings are set to default. I've got one of these boards from ASUS and occasionaly for no reason at all it just resets the boot settings to default. Might be some sort of fail safe but seriously annoying if your OS is on your RAID drive. Just need to nip into the BIOS and do this:
1. Select BOOT menu,
2. Highlight Other Boot Device
3. Press enter and select SCSI/Onboard ATA Boot Device
4. Use the + key to move it to the top of the boot list
5. F10 to save changes and exit
HTH