Further testing ... It's a tedious process to track bug as there might be multiple factors that might be contibuting.
I have multiple screens. Opening the example room i downloaded (http://www.sweethome3d.com/examples/userGuideExample.sh3d) works fine but some drawings i've been doing don't ...

Think i found the solution ... i had a 0 thickness shower tray. removed it and now it's almost ok. I can't get the 3d view back to main window but the 3d view is working ok in a seperate window
i will post an abstract of log, if it helps ...
Exception in thread "AWT-EventQueue-0" java.lang ...

i got the same problem. Using different versions doesn't solve the problem (windows 8, archlinux (AUR or bundled version of sh3D)) i can post my saved file to test.
BTW thx for the great work