Creat a new folder inside your "mapname" folder and name it texsrc then put your clipboard map in it after converting it to 256 color (aka indexed color, 8 bit color).
To find out why it's crashing there's a button under the objects tab for error checking, some errors are harmless, for instance you will always get a runway touches gridline error for every field, just make sure they dont cross a gridline or they will apear chopped off from some angles.
