"No, I can't do that yet"

Since the patch I've been getting occasional "that's still recharging" messages from my characters. At first I noticed it happening when casting portals and teleports on my goblin mage - he'd cast the spell just fine, but he'd also say "nah that's still recharging". Then the same thing started on my draenei mage, and now my troll druid just told me that while I was autoflying - meaning I didn't even touch anything (on the mages I'd suspected maybe the game was trying to cast twice or something). I asked my friend if he'd experienced the same and he said yes, on his priest.

Does anyone know why this is happening? Is it a bug in the game or is an addon perhaps known to cause this sort of thing? It's a minor thing that doesn't affect my gameplay, but it's still something that shouldn't happen.