I have this issue. I had this issue with my first Vibrant last year. Samsung replaced that one, and the new one didn't have this problem for the first 10 months I had it. I've been trying to update the software recently, and managed to Odin back to the stock Eclair OS, and now the heating/battery draining problem is back. I'm hoping that if I complete the upgrade to Gingerbread, this problem will stop, but who knows...