I reluctantly replayed the entire 7th chapter from the beginning after experiencing a game killing freeze-crash which occurred right after the cutscene after defeating the Alpha Ceph. I was initially too mad and worn out from the long struggle of that fight to re-try it. Reloading from the last checkpoint was no good because it would continue to re-freeze. So I waited a couple of days and replayed the entire chapter and this time after defeating the Alpha Ceph the game continued normally all the way through and did not freeze up! Yes . . . I am much happier now naturally.
I am playing on an Xb360 but I know that this 7th Chapter freeze has been reported on PS3 and PC as well, so I hope this message reaches all of you that have experienced this. I will also post this message in some other places to try to reach more of you. I hope this helps some of you to not totally give up on the game as I almost did.