1) This is the wrong forum. I'll move the thread for you, but next time please read the forum descriptions before posting.
2) Did you download an update for QuestHelper or Cartographer3 recently? If so, try downloading the version you had before that.
3) Does the problem still occur if you log in with only Cart3 and QH enabled? If not, did you download any updates for other addons recently? If so, try disabling those addons one at a time; if the problem goes away, post a bug report against the addon causing the issue.
4) If neither of the above apply, your next move should probably be to post on the QuestHelper page, since its author is not active on these forums and is unlikely to see your posts here.