This is a rather annoying bug that I wish would get fixed. It's probably one of the top ten worst bugs in this game.

I've had it come up with numerous characters of various races both in and out of combat. It's happened when using two handed weapons and dual wielding, not so much on sword+shield but it does happen. It's happened after switching weapons. It happens after blocking, dodging and interrupting enemy attacks.

And it's not limited to melee or weapons. I've had this bug pop up after casting spells, both offensive and defensive, single target or aoe. Words can't express how obnoxiously frustrating it is to be the team healer and have your skills suddenly lock up.

It will also come up if your character can't path properly to an enemy when using a charge attack like "critical charge", "dragon leap" or the WW's "pounce".

I've used three different keyboards (Razer Black Widow, Logitech k800, and an old Dell keyboard I had from a few years back) to see if maybe that was the problem but it seems to be happening universally across all three.

It might be an input issue. It seems to happen most often when I tap a key several times or when I'm casting a lot of spells in succession but once again it's not always consistent. Sometimes it just happens clear out of the blue.