I know the problem the person is going through as I am going through as I was and still am going through the same. A factory reset does not help and even when I kept doing it i tried two ways. The first I allowed for Google to restore my stuff but it still happened, the second time I didn't allow it thinking that perhaps it saved something damaging. It happened once again and it has been rather frustrating even sometimes it would cut me off of calls or not allow me to call for some reason.
Something I did notice though is that if you close everything ( I was looking through the Go! Taskmanager as well as the regular task manager). I find that the phone is setting at 50% and I have no way of knowing what exactly is running in the background. It's also frustrating finding that the phone has locked itself up and has to be rebooted (taking the battery out and all of that) and even doing so does not completely ensure it will turn back on as sometimes it will simply freeze itself on the Google logo.
Overall ICS started out well but it wasn't until recently that the problems manifested themselves (at least for me). So not sure what to think about it overall and have been thinking back as to what may have caused this problem but so far I have encountered nothing and am unsure as to what the problem is...