KA1: web page protected with htaccess not accessible

Hi there,

i manage my library with calibre but i don't want to carry my whole library on the device so i set up COPS (http://blog.slucas.fr/en/oss/calibre-opds-php-server) on my private server which will be synced every time i modify my library in calibre.
to make sure that COPS is not exposed to public i protect the page with htacccess.

thing is, that i cannot access COPS cause i get no authentication prompt using my KA1.
error msg (no htaccess popup before showing the msg):
its working fine using my kindle voyage (or any other kindle)
any ideas what i could possibly change/modify/re-configure?

any help is highly appreciated.
Ron