Problems modifying stock maps

[Giftheck]

Hi, it appears I have some problems modifying stock maps. If I try to modify certain maps in ZeroEdit they tend to crash when I test them out. Certain maps I can modify but have to do it by manual editing of the layer files in a text editor. Others just flat-out do not work. The only one I have successfully modded was Naboo Theed when I converted it to include changes in the SWBF2 version. SPTest gives no reason for any crashing.