Lately my computer has been doing wonky things. The Windows repair program recommended doing a system restore to an earlier restore point. As I had been unable to fix it any other way, that is what I did. It was restored to a point before I installed the Fast Lane stuff pack. When I went to play after the restore, several of my saved towns won't load. The box has the generic people outline picture, and when you try to load it, the message "A serious error has occurred while loading 'twinbrook.sims 3' It is strongly recommended that you restart the application."

There is also a second box that is blank titled "twinbrook(55) that has no picture or icon in the box. You can't click on it, and when you hover the mouse over the box, the message says "Cannot load this save game. It may have been saved with expantion pack data that is no longer present on this system."

Two files that I had not played since installing the stuff pack before the system restore are not effected.

I tried uninstalling and reinstalling Fast Lane stuff, but it did not change anything. Is there any way to get the files back?

Most likely the registry is now messed up with the restore, uninstall, reinstall.
Run CCleaner to try clean that up. Game_Help:TS3_Uninstall#Cleaning_up_the_Registry^wiki

Do you have a .backup file that you can restore? Game_Help:Restoring_Backup_Saves^wiki
Otherwise, I don't think there is any other way to salvage that borked save. Even if you do, the game may be glitchy...

Worse comes to worse, you might need to do a full uninstall & reinstall as per the Uninstall FAQ linked above.

And if the computer does any more wonky things, you might want to diagnose that. I can move this thread over to the Computer & Software forum or we can lock this and you start a new one there with all the pertinent info. Only way to ensure the game is not made worse by a computer hardware issue...you can post Game_Help:System_Specs^wiki, if you want to get that started.