wannabhermione - there are a number of issues with pets that were were corrected by post-release bug-fix patches. I don't know with absolute certainty, but there may also be some issues regarding post-pets expansion packs not behaving well because there is content that may not be properly activated in the absence of pets when they were installed.
Both of these problems might be resolved by unistalling all your EPs back to before Pets EP and then re-installing the EPs in their order of release. The EA tech manual recommends the following installation order for the PC-version of the game:
In any event, please make certain to preserve a copy of your downloads and other save folder data (e.g., neighbourhoods, savedsims, etc) in a secure location outside the Documents folder during any un-install, install, or update process. Remember, uninstalling any portion of the game will result in all saved game data (including downloads, neighbourhoods, savedsims, etc.) being deleted!!
