If the map denies access to the map completely, it has been protected.
Unless you have the makers password, and a map protection type program, save your energy for a new map of your own.
If the map opens, but tells you that ?? units were unplacable, and were deleted, I would suggest the X-tra Editor.
Best you'll find, or ever use.
Find it at this page.
http://www.campaigncreations.org/sta...ms/index.shtml
The rest comes with experience.
Good luck,