I was having the same issues. My phone was locking up all the time. I would be on the internet and a call would come in and my phone would not let me answer. I took the phone into the Verizon store and they shipped a new phone to me. I plugged my battery from my old phone into the new one and started having problems again last night. So.....today at lunch I went back to the store and they agreed that I had a battery problem. I'm just charging the new battery up right now and will see if I have any issues. I had the store reactivate my old phone. I've protected it in an Otter Box since I got it last year. No scratches and I have never dropped it. The "new" phone that was shipped to me is used, has rubbed edges and was not taken care of like my phone. I'm hoping the new battery is the solution.
If you can take your battery out and try to spin it on a flat surface you can tell if it's still good or not. If it spins....it's bad (warped). Also the tech at the store said the batteries are only built to last around a year.
hope this helps, and I'm crossing my fingers my old phone works like new. If it doesn't I suppose I'll go with the "like-new certified replacement" model.