one hour later....
dear George - dear Richard.
well i was pretty sure (!!!) that there no php-bug can cause such errors:
this idea here - you mentioned did not make any sense to me.
Unfortunately, due to the PHP errors on the current site and the lack of Debug output, we are unable to see what the issue is (our plugin doesn't load correctly, the Help and Status tests do not operate.)
no - there were other things not workin correctly.
imagine: all the other facebook-plugins run well - only one does not: i had a closer look at the variables...
the setup was wrong: ik-facebook had the wrong customization - in other words: i had to correct the facebook page-id
i did i with the following helper-text how to find your facebook-page id: http://findmyfacebookid.com/
and entered the data here http://www.ex-libri.org/wp-admin/admin.php?page=ikfb_configuration_options
i entered the correct page-id: 3241300409xxxx
NOW I have results - it works <- i try to customize it so that i can get the aimed (and whised ) settings
many thanks for all your help