Agree one of the rails is gone. In a general way you have a 12v, 3.3v and 5v output in the PS. One has gone bad. Probably "took some heat" from the bad cord. Here is a suitable replacement (http://www.newegg.com/Product/Product.aspx?Item=N82E16817341048).
It has gotten vg reviews and is efficient. It will give you a bit of power headroom so if you upgrade a video or othe item you will be covered. There is a 750 also if you think you are going big in the future (like a complete system build replacement). This is the OCZ "budget" line but is a good choice.