my iphone will no longer pair with my blue ant st3 bluetooth

We just upgraded an ipone 3 to an iphone5 and it will not pair with our blueant st3 bluetooth. My iphone4 is paired with my other blueant st3 and works fine. If I go into settings on my iphone4 and selett bluetooth it tells me the device is not compatiable and asks if i want to forget the device, after I reboot the iphone4, all is well. My iphone4 is running V6.0.1 and the iphone5 is running V6.1. Any suggestions?