post-new.php not loading

I can not make any new posts and pages, neither can I added them. I noticed this problem after updating to 3.5.1

What did I try so far:
1. I did disable ALL the plugins > no success
2. I did a new install of 3.5.1 through the backend > no succes
3. I renamed the wp-admin and wp-includes folder manually through FTP and re-installed those folder through FTP and ran the update page > no success

I CAN make new posts with my mobile though using this app: https://play.google.com/store/apps/details?id=org.wordpress.android&feature=search_result#?t=W251bGwsMSwxLDEsIm9yZy53b3JkcHJlc3MuYW5kcm9pZCJd

Also the plugin ‘Guest posts’ works but neither solutions are ideal.

Can anyone help me to get this running again how it should be?