Look at the origin. Are there "phantom entities" there?
Press L and select these entities. Delete them then recompile.
These "phantom entities" appear when a previous entity member is turned into a new entity. For example, I create a brush, select it then make it into a func_door.
I then decide that the door needs more detail. I create some more brushes, select them and the original door brush then make them into another func_door.
The original func_door is now empty and in Radiant 1.5 appears at the origin. It can only be selected from the entity list. This is why the select all and copy method works.