Hi mjarnit,
It looks you are running old version of Wp(3.5). Like the other members said,try to update your wordpress. your can do it in several ways. for example if you installed your wordpress by using any 1-click instillation application,then you can update it from your hosting cpanel,as the hosting provider will provide you the update.Perhaps you should contact your hosting provider for help.
if you are going to re install your wordpress manually,then take a back up of all files including important file like wp-config.php,theme,database backup and then update the wp as per the above wp documentation link.
in some cases you will get blank screen in wp-admin due to whitespaces in functions.php .if that is the case take a look at your functions.php file and make sure the are NO spaces at the top or bottom. Also Try to increase memory limit in php.ini
Cheers
