I know this defies logic, but several times when this has been reported in the past, both bulbs were bad.
-RP
I'd look at the fuse first, the bulbs second, and the circuit last (in the circuit, a weak point is the starter switch), as those priorities take into account probability of failure as well as ease of checking (ie, check the easy stuff first). As RP says, bulbs often go out together, as they usually have the same age on them, and they may have been taken out by a voltage surge. Just recently I lost both 50watt spots and my low beam within one day, on my standard.