Theres alot reports about this going on, it appears to be occurring primarily from button mashing on complex macros (something multiboxers will do often) theres a couple of blizz forums about it at this point, first of which has a blue response

http://forums.worldofwarcraft.com/th...860055&sid=1#5
http://forums.worldofwarcraft.com/th...91121547&sid=1
http://forums.worldofwarcraft.com/th...93801&sid=1#30