Can't change lay out sidebars??

I’ve got the lay out whit left and right a sidebar but now I like to change it to just one sidebar.
But the lay out options are not working anymore???

I’ve allready set to default and import my things again but still can’t change.
Also deactivated all the pluggins and updated wordpress and the mantra theme.

Hope some one knows whats the problem.

Greetz from Sam of the Netherlands