Second the above as the most likely cause if low-voltage lights. If they're regular 120V types, or if the power unit for 12V types is fine, then it could be a loose connection somewhere on the feed. If those two lights are on their own switch which controls nothing else, then it could be a bad switch. Presumably you've checked for a tripped circuit-breaker or blown fuse, although if that is the cause you would have probably noticed something else not working by now as well.
Check also for a tripped GFCI receptacle - It may be the bathroom receptacle itself, or it may be somewhere else in a different room, so go around and check any and all.