Computer takes 4-5 boots to work

Here is a weird one. I build PCs from the ground up.

Current box has this setup:

AMD Phenom 9950 Agena 2.6GHz 4 x 512KB L2 Cache 2MB L3 Cache Socket AM2+ 125W Quad-Core Black Edition Processor
MSI K9N2 SLI Platinum AM2+/AM2 NVIDIA nForce 750a SLI ATX AMD Motherboard G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500)
Windows Vista Home Premium 64 bit
2x WD 78 gig Raptors Raid Zero

For almost a year this PC has worked flawlessly without any issues.

Problem:
(Boot 1) computer turns on, hard drives don't start humming (Power off lets all fans come to stop wait approx 10 seconds)
(Boot 2) turn on - hard drives start going, go through post, get to desktop. Approx 1-4 mins (varies) Monitor goes blank - computer still going but doesn't seem to respond anymore. (Power off lets all fans come to stop wait approx 10 seconds)
(Boot 3) same as Boot 2
(Boot 4) same as Boot 2
(Boot 5) Finally monitor does not go blank at desktop. Computer works just fine.

Very very problem that I have never encountered before. Any help folks?

Thanks,
Jason

Try this procedure to see if you can find the culprit: Hardware Troubleshooting Via System Stripdown

Get rid of the RAID when first starting out. Use each of the hard drives separately. Test them together.

Will do. Will post results when I have them.

Thanks