Since your game resources in v0.5 (and later) of RPG in a Box are stored differently, you'll need to go through a simple migration process to convert your project when moving from pre-v0.5 to v0.5+. This page will walk you through the necessary steps to get your game project migrated to the new version. Since v0.5 is currently in an “incomplete pre-alpha” state, this is more for testing purposes right now and you will most likely need to follow this process again once it has become stable.