Try a new set of batteries, standard nonrechargable ones, if the problem persists scrap it and buy a new one.
You can buy better new ones for a lot less then that one would have cost. You can get get a good Canon quite cheap, depending on how much you want to spend.
Here's one for $84 >http://www.newegg.com/Product/Product.aspx?Item=N82E16830120390