Exporting non-square maps

hi there,
ive been trying to export a 256 x 512 heightmap in the official map editor.
i have done it before quite a while ago, but somehow it is not working right now.
exporting square maps does work.
this is what i see when i open the exported map in photoshop:
width: 514
height: 513
channels: 1
depth: 8-bits

when i change the settings to how it should be (16 bit IBM PC) i get the error that the image is larger than file.
when i open the file with the startup settings i see some really weird image where you can see the shape of the map if you loook hard.

basically this problem is part of a bigger problem of when i tried to change something to fields of isis:
i exported everything in fields of isis, made a new map, imported everything again and started editing some stuff.
then, when i was done i put in the code that would change the playable area of the game.
when i did that, basically the entire map broke. i tried to remove all the playable area stuff again, but one problem remained: the water ingame had the basic colour instead of the colour i made it in the editor (colour was right on the minimap)
i checked that last story with a second test, i did everything as said in the turorial but it broke the map.

if anyone can tell me how to make the playable area stuff working that would be perfect, if not please tell me whats wrong with exporting non-square maps.
thanks in advance,
Leo|||Try making the map (and hightmap) square, but just using areas to blacken out the part you don't want to use.
GreetZ ThaPear|||thx for the reply,
but if you read my post before you reply youll know that setting playable area brakes the map too.|||it is still not working!
this is the map file: http://www.filefront.com/16626927/Impact_Isis.zip
someone please help!!