Taric E activation delay

Last night I was playing Taric and his E (stun) wasn't activating the way it usually does.

I use smartcast, and usually when I press E the spell activates immediately -- as soon as I press E the stun field appears in the direction of my cursor.

But last night, whenever I pressed E, a little animation of the stun field would appear (as if I didn't have smartcast on), but the spell wouldn't activate immediately. I had to press E and hold my right hand cursor in place for a second, then after a delay the spell would start. If I moved the cursor immediately after pressing E, the spell wouldn't activate. This made it impossible to activate E while I was chasing people, because as I was running and moving the cursor forward, when I pressed E nothing would happen...

Anyone else noticing this?