I am having the same problem.  I am using the work around of entering information on the Interest screen (Screen Page 11), and then making a note in the client files about the work around.  At a minimum, I think Lacerte should have a diagnostic about this until fixed.  

Also, if you do enter data on the interest screen in order to get the correct add-back in NC, be careful that the tax-exempt interest on 1040 Page 1 still reflects the accurate amount of total tax exempt interest because that will affect the clients' MAGI for calculations such as their Medicare premiums.