Bertier,
Is it freezing when you ask it to create the layout images? It doesn't surprise me if that's the case. That's a lot of groups for the plugin to calculate through to figure out how to lay them out on a bunch of narrow boards. It may be that you've exceeded the number of boards the plugin is capable of calculating, too.
Since you haven't added one of the "Sheet Material" words to the group name, the plugin is trying to do the layout based on the groups being made from solid wood. Is that what you are intending? Or should they be made of sheet goods?