Looking at the changes in 0.6.0 I think this problem was just hidden in the previous version as resources were not released properly    

private void releaseTransaction() {

        -//TODO: release non crucial data structures to preserve memory?

        isOpen = false;

        graph.closeTransaction(this);

        -vertexCache.close();

        +vertexCache = null;

        +indexCache = null;

        +addedRelations = null;

        +deletedRelations = null;

        +uniqueLocks = null;

        +newVertexIndexEntries = null;

        +newTypeCache = null;

    }