Gameplay Bug

I have had 2 ranked games as Darius where he becomes unable to auto attack, he just circles attack targets, both games I was using Dunkmaster Darius, so this may be a skin related issue and not a champion issue. I have had several games in between these two games, using Darius and the skin, where there was no issue, and then it reappeared again.

The first time it was against Garen, and the second against an Amumu. It only happened against Garen when he got his 'w', and Amumu at level 3, which I assume he took his 'e', no reason for him not too.