Hi girlieworks,
thanks for the prompt reply. I set the WP_DEBUG to true, however blank screens continue. I have no clue how to check server logs, but I created a ticket to my hosting provider.
By the way I was playing around and renamed:
wp_content/plugins-> wp_content/plugins_tmp and
wp_content/themes-> wp_content/themes_tmp
Now all three pages started work, but of course now the main page went down. I deduce that these 3 pages require some special handling.