A map with a file size of 1 KB.

I remember reading somewhere about a solution to this problem...
I don't recall what they suggested, but I'll just say that the issue probably isn't related to the path to the map. In the HoMM 5 Gold Edition editor, any map gets corrupted, regardless of what the map is or where it's located. However, in version 3.0, the editor works fine. I think the problem lies in the editor itself.