This happens almost every day for me though it's not too common; maybe 2-3 times a day, but it is a bit annoying when it does happen. Occasionally, when I'm in combat, my skills will just stop responding when I hit the correlating key and I can't swing my sword when clicking either. This isn't due to stuns, snares, etc. I found that this is easily fixed by hitting c and bringing up the character menu; after closing the menu, my attacks work normally again.
Not a big deal, but I think it should be brought to attention nonetheless.
QQing is a full time job