I bought my V6 brand new in May 2010.

It has over 14k miles. I recently noticed after brake is heated (afternoon traffic), the brake will make noise when I step on the gas to go from red light or stop sign. I am guessing the pad is rubbing during the first few feet as I step on the gas. It does not happen when brake is cold (first thing in the morning). The brake pad is still quite thick.

What could be the problem?

 

I think you already stated eat the potential problem might be. Take her in and get it looked at; it's under warranty.