Just to add my two cents: the exact same thing happened to me with the latest EP intstalled, and I finally managed to fix it by, in addition to deleting all my custom content, deleteing all 5 cache files in ~\Documents\Electronic Arts\The Sims 3\ - the CASPartCache.package, compositorCache.package, scriptCache.package, simCompositorCache.package an socialCache.package files. I don't think the deletion has any negative effect on the game, apart from it having to generate them again, but if you want to be cautious, just try renaming them.