that is because normally the freeform unlock only workes on new games. So if you save and start again, freeform unlock does not work (usually) :crying .
If this is not the case and you don't have any problem on one of your other saved games, please try and re-install the game. Do not uninstall first, but just re-install over the exsisting game. This way your downloads and save games will stay where they are and all the *.dll files will be renewed. Sometimes this helps.
If you still want to do a complete re-install (so uninstall first and then reinstall), please be sure to save your downloads and zoos somewhere on your computer. Then when you are done, put them back into the game.
Hopefully this helps