Brief
We have modified the 'admin_layout.php' file after release 3.4.2 has been issued.
 
Description.
While creating a new layout you could have received the below error:
Database error: Invalid SQL: INSERT INTO va_layouts_sites (layout_id, site_id) VALUES (10, 1)
MySQL Error: Duplicate entry '10-1' for key 1
 
Solution.
We would recommend to download an updated version of the files from here: http://www.viart.com/downloads/admin_layout-3.4.2.zip
 
Further, extract the above mentioned files into the 'admin' folder of your shop replacing an existing one. Don't forget to make a backup copy of the current file in case something goes wrong.

I was having problems so i inserted this patch and now the make active buttons do not work when moving to other layouts..
 
I recoment backing up your databse before, trying to add layouts because I had to restore it, after somethinh broke when checking adding new layouts etc..