After I told the Chieftain's son the cure about the Illness, every enemy stopped attacking!

They see me, walk towards me, and then it seems they walk against a blockade. They keep walking (or try to), but don't move an inch. And I can kill them without any problem. This is no fun!!!

Can anyone tell me what is wrong? And please, a cure for this problem <img src="/ubbthreads/images/graemlins/cry.gif" alt="" />