This happened after install the v1.03 patch: in story mode, guns work as normal for a few enemies (or perhaps for a few minutes in game time)and then it just like shooting blanks, no longer works. Reload checkpoint and just the same old story. The weird thing is that in this time, enemies actually ignore my presence, eventhough I was right in the open. The only working weapon would be grenades or anything that'd explode.

Now, before the patch I've some A.C.E.S points in excess of the lv 20, so after the patch, under the new system I got some more XP points awarded. I reckon this has something to do with it.

I've tried to reinstall the game and just patch to 1.02 but it won't work either.

ok first of all they have quite a few problems sorr i can't help there but with the new xp systeam you get xp after the other ranks i.e the one before 1.3 came in