I noticed that this happens to me sometimes as well. Make sure you click on General tab in the chat couple of times. If that didn`t help - try restarting the game, sometimes that fixes the problem.
Now if even that doesn`t work - you`ll need to follow these steps to reset Chat settings:
1) Click on the organizer button in any folder. And select Folder and Search options. Go to view, and under Hidden Files and Folders, or Drives - click show hidden files.
2) Now navigate to C:/users/YOUR USERNAME/AppData/local/DoF/
3) In that file, locate and delete file called local_saved_data