create Maps

everytime i try to make a map of our environment, the whole realm server crashes down. especially of the one grid quare where we have a building which is 256 bocks high. after one server crush our best horse on which i was riding on disapeared with saddle and it's diamond armor! that really s*cks!
and now even when i'm far away form that building and walk around and try to make a map of a natural environment the server crushes.