although not raid related, I have a similar problem.
My D630 laptop with an SSD drive installed won't boot from the drive during a cold boot.
After power on, it says drive not found and after a warm reset (ctrl-alt-del) it finds and boots the drive just find.
Even if the BIOS is up to date, it's most likely the motherboards fault or the add-in card is taking too long to initialize. (yeah, that's vague, sorry.)