I have this error in all folders except in "Buildings". Do you know how can I fix it?
By the way, great job, I like Asset Forge very much :D
Sorry you've encountered this, it's a bug in the system that generates thumbnails. You can try removing the thumbnail cache by going to the settings and clicking the button to remove the cache (you might need to restart Asset Forge), if that doesn't fix it please report back so we can fix it in a future release of Asset Forge :)