Dashboard > Appearance > Widgets not working

Hi, Maybe this my request might not be theme related, but I have problem with my Wordpress Dashboard >appearance > widgets. I can't add any widgets to my website. The widgets area is blank (wordpress in Finnish-language): http://sapa.fi/wp-content/uploads/2015/01/WP_Dashboard_Widgets.png Also when I press "manage.."-button on the upper left side, it shows a blank page (Some link to the Google Analytics Stats (which doesn't work)): http://sapa.fi/wp-content/uploads/2015/01/Edit-Add-Google-Analytics-Stats.jpg I googled about this problem and only found this topic: https://wordpress.org/support/topic/the-dashboard-widget-area-not-working-correctly It sounds like I might have the same problem as the link above. Do you have any idea why this is happening? Problem with WordPress? d Any advise appreciated. Thanks. -Juha