Please provide more info;
What version is your RME, what version is the map?
Have you been able to open up the map before?
If so, did you do anything to the map at that point?
One thing you can try is to create a new map(file => new), import the "bugged" map (File => Import => Import Map => Click broswe and nagivate to the map, then hit OK).
See if you can open the map up now, note it might bug if the map is ex 10.98 and your editor is 10.76 (due to missing items from those updates).