>* .ik myfilter.keywords

That shouldn't work.  The syntax is simply

* .IK <filename_of_keywords_file>

ie,

* .IK MYFILTER

You aren't supposed to specify the .keywords extension, as it is assumed.
(It could be that LISTSERV simply ignores everything after the dot; I
haven't tested that, but it isn't <supposed> to work that way.)

Nathan