Ned with fail-to-save maps hog up space

[w95559w]

http://i.imgur.com/qvTgntw.png

Just like what you see, there are 6 level with (level data not found), and I can not perform any function on it. If this continue on it will eventually take up all 10 space and I will not be able to publish any map, due to there can only be 10 maps in Ned. Please help me with this, thank you!