Someone else had the same problem on another topic/thread.  See their text below:

 I need to create an additional forum.  I have the "General Forum" that I configured to the way I wanted and now want to add another new forum.  I am under settings>>forums tab>>all forums...on the list is the one forum I have created and in the top right corner is a button that says New Forum.  I assumed clicking on this would provide me the form to create a new forum, but instead clicking it clears the exisiting forum form that was showing, you see the loading icon and then all is blank.  What am I doing wrong?  (using IE browser)