I'm not sure that changing the grips without figuring out if they are improperly wired is a good idea. The only experience I have with heated grips is with my Oxfords, and wiring them was pretty straightforward. i would check over yours first. I would expect that one side or the other might fail, but not both at the same time. Your problem sounds like either a bad wiring or more likely a bad controller.
You might hook one side up directly to the bike (or the bike's battery) with a fuse in series. If the grip heats then it is probably the controller or the way you had them both wired. Then check the other. I don't know if one bad side would affect the other one, but checking them independently will tell you if they are good in a very short time.