The next thing is to see if one of the savegame files has gotten corrupted, which can happen if the system or game crashes. Go to Library\Preferences\LDW in your home folder and locate the folder called Virtual Villagers - The Tree of Life. Rename that folder (putting a letter or number in front of the folder name is fine). That way, the game will not try to load the existing savegame files. If the game loads OK, then one or more of the savegame files is unusable.
There are a couple of ways to handle a corrupted file. If you weren't very far along in the game, the easiest thing to do is to delete that folder and the game will start clean, as it did when you first bought it. If you want to try to save your progress (which may not be possible, depending upon the condition of the files), you will need to remove the savegame files from that folder (to another folder of your choosing), put the folder back to its original name, and start moving the savegame files back into the original folder one at a time until you find the bad one. That file will need to be deleted in order to run the game.
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Barbara
Unicorn
Last Day of Work