Motorola Droid 4 :: Unable To Answer Incoming Calls?

Ever since my phone was updated to ICS, I've noticed that once in a while (it's probably happened 5 times now) I can not answer an incoming phone call. Usually it's while my phone is in the Droid 4 car dock, but it has also happened without it being connected to anything. What happens is my phone will ring either through the phone speakers and my bluetooth headset (if connected), but the phone "answer" screen will not pop up, and the phone doesn't respond to any type of input, which forces me to reboot my phone by holding down the power/volume down buttons. Once the phone boots back up, there is no record of who called me in the recent calls list, so hopefully they leave me a voicemail otherwise I have no idea who called me. After the first couple times this happened, I decided to perform a factory reset, hoping that this would fix the lag/freeze up issue, but it did not correct this problem. The only way that I can think of trying to minimize the occurrences of the phone freezing up/ running sluggishly would be to perform a reboot every couple days or so to clear up the memory.