I made a copy of my "Neighborhoods" folder, but when I restored it and started the game all the neighborhoods were gone, even though the folder size indicates they exist. Is there a trick to this?

- Update -
I got my neighborhood back, but I'm not sure exactly why this worked. I restored an old backup of the "sims2" folder, the neighborhoods as they existed 4 weeks ago were there. I then copied the newer Neighborhood over the old Neighborhood. All the neighborhoods disappeared again. I then opened the newer Neighborhood in SimPE, didn't make any changes, didn't save anything, and exited. For some reason, my neighborhoods show up now. Maybe it's a fluke - maybe SimPE actually did something behind the scenes. Either way, its okay now. Next time I'm backing up the entire Sims2 directory and not just one folder.

I had the exact same thing happen, although I think mine's because I have some files from Pets there.