Did you happen to download a hack (pre OFB) that enables custom food to "
disappear" after sims ate it? I do know from experience that particular hack was buggy as all get down. You may have it in your game and not even know it, especially if you are one that downloads custom lots every now and then from the exchange.
(The sad truth is if you do download from there, you've definitely downloaded a hack along with a lot. Try searching your downloads folder with either
Sims2Pack Clean Installer or
Delphy's Download Organizer and see if you find any extra hacks hiding... they're usually highlighted red, so they're not too hard to find.)
