I had the same problem. I started to doubt my gaming skill. I tried for like 25 times. I wasted my ammos, health packs to kill that beast. Then I remember I had the same problem with Dead space 2 and only solution I got that time was to lower the graphics option. So I gave it a shot in Dead space 3 also and it worked. If you haven't found any solution and haven't tried this solution, then try it first. If your problem is solved then its good, otherwise you have to wait for a better solution.
Thanks a lot. That was really the problem. I lowered the graphics and it worked instantly. Great.
