both gnus and flim define "mailcap.el". the "wrong" (for gnus) version gets loaded, resulting in no "mailcap-parse-mailcaps" function, and emacs refusing to read news items with certain MIMNE headers
Sorry for replying late. >=flim-1.14.5 doesn't install mailcap.el and I've just removed (old) <=flim-1.14.4 from Portage tree. Please report back if you still have the problem.