Well , after the guide gaven by iSean , i did make a few pvac myself until recently , i couldnt even render the map using the harepacker gaven by iSean , the screen shot below might explain it all .
The issue lies with maplestory. It is currrently "locking" your map.wz. Hence you will not be able to write to map.wz. Try saving it as other filename, and I bet with you it works.
You may say you are not running maplestory. Problem is that you already ran maplestory, and quitted it. I see your hackshield program still there from the bottom right hand corner of your SS. Note that quitting maplestory does not really terminate its process. Ctrl+Alt+Del and you still can see maplestory.