I agree that a dead battery is the most likely culprit. Try a new and fully charged battery and check the battery contacts.
If the battery itself is not the problem, remove both batteries from the camera. Your manual should describe how to remove both the NB-2LH battery and the back-up battery used to power the calendar etc.
Leave the camera sit for a half-hour or so and then replace both batteries,
Then after sacrificing a virgin (if one is readily available) to the Canon Gods; turn on the camera. By the way, crossing one's fingers often does as well as sacrificing a virgin.