My clients site has been experiencing some issues lately. It seems to happen randomly and I have confirmed that neither her or I have been making changes to the pages where we see this happening. Expired products, and active products will just show up on pages they have not been assigned to. For example http://www.artandsoulbeads.com/store/metal_fill_beads.html - This page was showing over 50 products, which has now been reduced to 3.
Whenever this random product thing happens one of us has to remove each product individually under Assign Product to Pages. A very long process.