New Post: Multiple catalogues on the same site

Hi,
on this topic I have started to work on the same catalogue, creating new top level categories and using nbstore product and category modules on new pages. All looks ok, but today I discovered that all the images not belonging to the catalogue in productimages were deleted. What could this be due? Is there any relationship with the dual catalogue or is just a 3-month cycle log purge which perhaps involves non-listed images in that folder? If so, how can I prevent that?

Thanks

Franco