Did you actually leave this as it is written in your email?
define("NS_FOO", 500);
define("NS_FOO_TALK", 501);
if so try:
define("NS_HISTORISK", 500);
define("NS_HISTORISK_TALK", 501);
another thing which helped me was to change the name space number from 500 to 1000 and the
NS_TALK space to 1001 leave everthing under those numbers available for Mediawiki