changing themes gives whitesceen on all links(subpages)

My site https://www.jonasb.no is working perfectly, (in my noob eyes) with Nova 1.1 av Elegant Themes
But when i change the theme, all the pages go white exept frontpage and admin.

I have tryed
-Chameleon 1.9 av Elegant Themes (which is the one i want to use and very similar to the one i use)
-Etherna WP 1.0a av evgreen
-U-Design 1.2.1 av Andon

however

“Twenty Ten 1.2 av the WordPress team” works

I have tried disable all plugins does not help.
I have tried change post styles does not help

other possible relevant data:
recently had malmware and walked the step listed here https://www.ads-software.com/support/topic/malware-on-my-website?replies=26
removed blanks from config file and .htaccess and more. But google has accepted my page again and i cant see or feel anything wrong.

Any suggestions ? ?? Thanks