Get a screen capture utility and have it running minimized, when you get the location you desire in Ogres mapmaker do a screen capture and use it to make the clipboard map.
I use
Irfanview to capture and Photoshop to edit the capture to a 512x512 8 bit 256 color bmp. You no longer have to use 4 256x256 squares for the clipboard map.
Then using the terr.bmp in the AH editor directory I make sure the bmp I created lines up. Resize the terr.bmp to 512x512 and flip it upright and align the capture.bmp, then rename to your terrains name and place in the terrains folder
The build problem your having is a bug, follow the work-around below.
Edit your terrain then switch to object editing then close the editor and save when prompted, close the application and restart it.
Re-open the editor, click edit objects and close and save again, then close the application - restart the editor then build your terrain.