Hey - i have set up my move+attack on LMB, everything was ok for me control-wise
I had what i wanted - having LMB constantly pressed to run around and attack immediately on pressing SHIFT.
Now i started the game and I can attack only when pressing SHIFT + then clicking LMB.
If i press only shift without a LMB click - it does not attack now, keeps running. Is there some button I pressed by mistake to cause this? 
Sorry for the noob question and thanks for your help!