In 6.1.00 there is a bug in the HERS calculation when the house has more than one block and no mechanical ventilation systems are entered. The file goes into a loop/freezes when creating the HERS reference house. This is a problem with HERS 2014 and HERS 2014(IAF).
Go to the Equipment>mechanical ventilation tab (MVent) and add a mechanical ventilation system with None selected under the Ventilation system type for EACH BLOCK. If this is not done for each block the HERS score will not be correct.