Custom materials list deleted when I change preset setting

Anytime you change from one preset (say Ambient Occlusion) to another (say Realistic-Interior) my custom materials list in the Materials Editor is deleted and has to be rebuilt from scratch. Is there a way to save a material or list of materials settings to avoid this problem?

Thanks
Matthew

Material settings are saved in the preset, so when you select a different preset the materials get overridden. To get around the problem, once you are done setting up your materials, save it as a new preset.