It's a long shot and due to recent instances I stopped suggesting it sometime after BV came out but... did you patch your game? I'm not sure if this was a problem in the latest EPs/SPs or not, but it definitely unnatural.
In any case, if you don't want the patch first, I'd suggest trying to copy over any/all files from your game disks to their designated folder in the Program Files' "EA Games" folder, especially your
objects.package files beforehand. There's info on what to do in
this link. If that doesn't work, then try grabbing the latest patch from the Sims 2 site and seeing if that works.
Hope it helps you.