You know how you have to hold Right click down for the laser beam? (not sure what it's called) I have move binded to my spacebar, so I alternate between spacebar and right click.
I'm not sure what happens but sometimes 'position' of the mouse gets stuck at where I last clicked (not sure if left or right matters). Say I was laser-beaming some mobs in the bottom left, now I want to move to the top, I would swing my mouse over and press spacebar, but the character goes bottom left and keeps going there.
The only way to change direction is to physically click on another spot, but then now that position becomes locked in.
When this bug occurs, I'm unable to move objects inside my pack as well. I guess it's registering as just a single click and not a click and hold. Sometimes, logging in and out solves the problem, but usually requires a fresh restart of the client.
Currently I've only experienced this problem when using a wiz and in archon mode. My main is a DH and I don't have any spammable skills on mouse clicks. (vault/MFD on left, gloom/smokescreen on right).