Rammus Powerball and the Krug camp

So a few times now I have noticed when I use Rammus's Powerball ability and go to make contact with the Krug camp, nothing happens. It continues to spin and wont cause damage. I wish I could create a video to show you guys what is happening, but my computer is not nearly nice enough to run screen capture as well as LoL. I was looking around the forums to see if anyone else was having this problem but I havent seen anything. I'll try to come back with more information and try to recreate the scenario a few more times. Any more info I could give Id be happy to share. Thanks guys!!