When Media Gallery is enabled, it replaces the
taxonomy_term_page callback on the
taxonomy/term/% path so it can present a better page for galleries. This prevents any module from overriding this callback, and it's a common thing to do with Views or Panels.
This patch adds a dependency on page_manager so that media gallery's callback is replaced only when nothing else will. If you use Panels to override your taxonomy term pages (the term_view task), you'll want to add selection criteria so that the media gallery collection list can run when the term is in the gallery collections vocabulary.
I am not expecting this patch to get in, but the way this feature is implemented now required me to build a work around.