Actually, I once got a message like that, without having protected my map. No idea why, maybe I shut down WorldEdit incorrectly or something. It fixed itself next time I tried to open it.
Thats the exact same quote it will give you if you try to open a map that has been protected. The steps needed to fix that would probably be the same steps needed to fix a protected map.
However, If its not even playable in game (on TFT or RoC), it may have somehow been corrupted, and if thats the case, then you are screwed. Always keep backups of your work. Thats one of the basics of map making. -VGsatomi