If you have Stark Mansion installed there is a minimap that blacks that area out to show the mansion on the map. Easy FIX: REOMVE the minimap
. CUSTOM FIX: EDIT minimap image with photo editor of your choice import back and your done. As the lad said the issues not with his map, its from another addon map. WORST CASE FIX: shut of every map and start them a few at a time until you replicate the issue. Then apply one of the fixes above if you wish to keep the map running.