Kingzacery, the solution to your dilemma lies in the previous posts.
But I'd like to explain it a bit further:
Reason #1: Map's Link: Please, open up your campaign and check your campaign buttons. Make sure the specific button that leads to the "Magic City" has the Magic City as its link. If it does, then please read the below reason.
Reason #2: File Corruption: In this case, the dilemma becomes more serious, as the only cure for this is a back-up file, so create a file titled something like "Backup Folder" and save your Alpha maps there often.
As was said before,if this is the reason, stop editing the current version and use the default back-up provided by the world-editor in the folder "Test", which can be found in the Maps directory.
If the problem still repeats itself, make sure all your data (map files and campaigns) is safe and doesn't have any bugs (Corrupt data, unreadeable memory e.t.c) Do this by constantly testing new maps.
If most of your data has this problem, there is only one solution left:
Re-install the entire game.
I hope this helped.