cant play new missions from mission editor.

[saunder]

Since the 1.5.6 update every time I create a new mission and try to start it I go straight to the active map, units start moving but that's all I can do and when try to close it I get a CTD. it happened on the first 1.5.6 update but I ran the repair option which seemed to resolve it but since the latest update the repair option makes no difference.