whow, Bob is really looking into it. It is very likely your Gspeed Raid (hardware) or the cable (we have never had any problems with SAS cables)
Definitely not ram (your computer would react totally weird and not loosing just the drive)
You can try Tech tool pro, a very good hardware check software.
My Instinct tends towards your Raidsystem.
Another Test:
I think you are on Raid 5 or 6. When your Gspeed is ready, pull one drive and replace it. It should rebuildt. If the Gspeed has a hardware error the rebuildt function should fail.
good luck
Rainer