I think I was the first person to have this problem, since then it's happened a few times to others... Maybe my stupidity is contagious? hehe.. Anyway, I think it's a loose jumper as tfabris said. Refer to this thread for what my serial bootup info looked like when I had this problem. If yours looks similar in the recognition of your drives, then your jumper is probably loose. Mine took two weeks to work itself a bit loose. I used some artfully applied electric tape to keep mine on, and it's been cool ever since. Or maybe get a jumper that is a better fit, there are different shapes and sizes out there.

-Tony
MkII #554