I hate to bring you bad news, but there's a chance SimPE may have randomly corrupted some resources inside your edited packages.
I first noticed this once while editing some skin files, where SimPe would show an error box while opening some of the property sets that I had edited. This would also make BodyShop crash when starting.
So far I haven't been able to determine what's causing this, therefore my advice is to keep your backups at hand.