First thoughts;
Check that the power supply does in fact supply 12v under load (these switching power supplies can, and do, develop a fault which allows the output smoothing capacitor to charge up to the rated output voltage - 12v - but the moment a load is applied that voltage dissipates and the unit stops working).
You did mark the locations of the drives otherwise you will have problems trying to read anything if you put them back in the wrong slot.
Do you have a reliable backup of you data? RAID 0 can be very problematic when trying to recover from the disks.
I know by now this is unlikely to give any reasonable result but you could try snuffing in the unit for a burnt smell which, if present, would indicate serious problems with the main board.
My first assumption is the power supply, second a burnt out component on the main board.