Just go into Video options in WoW and change it back to something normal, like 1280x1024 or whatever your monitor is set to.

For future reference, I think Keyclone modifies the config.wtf file for wow when it changes the resolution for multiboxing/maximizer. Rob can clarify that functionality.

There's probably a way to launch wow with a command-line parameter for resolution so you could just create a new shortcut for normal play but I can't recall what it is offhand.