I've noticed the same thing with Nasus and his Q. I'm going to post a thread about the same thing to give it more visibility, but I've upvoted yours, and will post my message to rito below:
Per the subject line, it seems that something changed with Nasus's Q today. The patch just went live, and all of a sudden his Q isn't always hitting the minions when I press it. Here's what I'm seeing: I'll press Q and click on a minion to hit. He will then walk up to the minion and stand still. He won't attack at all unless I click the minion again. He doesn't auto attack or anything. He'll just stand there. It's buggy, and doesn't happen everytime, but it's very noticeable when it happens. I'd say it happens about once every 20 Q's or so. I can't get it to repeat perfectly, but it caused me to die a couple times in lane because I tried to Q the enemy, and I just walked up to him instead. I got beat down pretty bad in ranked because of it. I couldn't trust the ability to work properly. I've never seen it before today. I don't think it's my computer, but I can't be certain. I'd like to rule it out by having you look at it. I tried to repeat the issue in a custom match, but everything seemed to work fine there. It's only happened in my 2 ranked games today, but it happened in both of them... several times each. I even shut down my computer and restarted and it still did it. Could you please take a look? Thanks.