When a solar system is downloaded and the designer is loaded beforehand, it causes a strange issue where the designer breaks entirely. There is no craft or anything, just a blank screen. Menus don't work. They darken, showing they are selected, but don't do anything.
Steps for replication:
- Make a random spacecraft
 - Exit SR2 entirely
 - Go to the website, and download a solar system
 - Wait for the system to download, and finish
 - The bug happens
 
                    
What system were you trying to download? Sorry for the delay but this being a suggestion made it totally slip through.