Having had the new expansion pre-ordered for me by my wife (for Valentine's Day) I finally decided that I was going to log back in to World of Warcraft, after months away, only to find that my Logitech G600 gaming mouse would no longer work.
I removed and reinstalled the software, just to be sure, and tested with my wife's (she has the same one) and it's definitely the mouse itself.
Shortest. Gaming. Session. Ever!
New hardware required...