Challenge your students, make them go away and do some research before they have the knowledge to solve the problem in the scenario. 

SBLi Server will let your students begin a scenario then leave it, for weeks if they want, and come back and continue where they left off when they have gained the knowledge to solve it.  No more "A lightening storm blew-up my computer just before I finished" excuses either, because their progress is saved on your server they can access it again from any Internet enabled computer.