Too few would be a problem, though the game is able to handle some missing files by replacing them with default versions (ie the now-fixed Map has gone back to black
bug in v1.33).
One person had the version number of the saved game become corrupt, so the game crashed when trying to load. He was able to fix it by hex editing one of the saved game files to replace the characters showing up as the version number with the expected values.
If the files/folder had somehow been marked as read-only, that would also cause the game to crash trying to load it.