Blast from the past ...
FWIW, I recently started encountering the same behavior.
Sometimes, the board (an MA785GMT-UD2H, rev. 1.1)
won't see *any* drives on cold boot (seems to hang
on IDE recognition, or whatever it's called).
But (at least for now) the drives are recognized
when I hit the Reset button.
Drive0 is a Seagate Barracuda ST3250410AS.
Drive1 is a Samsung Spinpoint F1 HD753LJ.