Any ideas?

Hi, I just noticed that when I download my residential lot (including custom content) from the gallery that I'm allowed to build and even play (to some extent) on the lot. However, I noticed that my sim will walk through walls, on water, and encounter several routing errors. Whenever I try loading back to manage worlds I'll either get an infinite loading screen or the world map will appear with an empty lot or with the previous lot that I bulldozed. Any ideas as to what could be causing this???