I had that problem with my first Radius way back in the day when they were first released, it would get really warm to the touch around the area behind the firing button. Then, it would drain itself while sitting on the desk without an atty on top, so Provape wanted it back to diagnose the problem which turned out to be a capacitor or something.One of the best. The only thing I don't like is it gets hot when recharging. Not too hot, I guess, but pretty hot.
Are you having the same problem when using the original Samsung battery? If so, it might be indicative of a problem that will need looking at. If not... hmmm.