Only occurs for me as the result of two things:

1) The temporal crap which causes me to desync.
2) Boldly They Rode.

Can fix it by popping open the character window, going to skills, and just moving the scrollbar up and down. Could probably do it on any scrollbar. With the first instance, it's not only a case of the mousetail but keybinds not working, etc, etc, etc - so I'll usually pop the character window open and hit up the scrollbar before hitting respawn.