Try selecting "File" - "New" then give it a name, size and all.
Then select "File" - "Save"
Then exit the editor
Then restart the editor and go to "File" - "Open" select the folder, and "yourterrainname.oba"
It Should be good then, if not try re-installing the editor. You do not have to delete or un-install it first.
AHEDIT2213.exe should be the current version.
midi