How to clear the game's cache
From Wolfire Games Wiki
Sometimes it can help to clear the game's cache. Here is how you can do that:
Mac
Delete the following folder:
~/Library/Application Support/Overgrowth/Data
Where '~' is your username.
Windows
Delete the following folder:
My Documents\Wolfire\Overgrowth\Data (NOT Program Files\Wolfire\Overgrowth\Data!)
Linux
Delete the following folder:
~/.local/share/Overgrowth/Data
