There are a couple of possibilities. One is that you've encountered a bug for which there's a fix. To install the fix, you'll need to completely uninstall Village Sim from your Clie (main memory and expansion card, if appropriate) using the Palm OS delete function before installing the fixed version. The savegame files are incompatible. To download the fix, click on the link for the fix:
www.ldwsoftware.com/VillageSimFixed.zip
Unzip it and install it on your Clie.
The other possibility is that your game has, for some reason, become corrupted. Deleting and reinstalling the game will correct that problem.