Laughing Man : I installed roadmap. It left my mime type active so it works fine for me, but i can see he installed a mime package for roadmap so you must be picking up that. So if you havent tried already, enable the application/x-gpx mime type in defaults tab and see if dbus-switchboard picks it up.

If you know you never want roadmap to pick up the association you can delete roadmap.xml from the /usr/share/mime/packages/ directory. you might need to do an 'update-mime-database /usr/share/mime' as root to take effect.

If you want to rig up a side-by-side association then you could rename all gpx files to gpx2 and associate with maemo-mapper... thats a hack because you will fallback to application/octet-stream but it would probably work (if maemo mapper was ok with that extension).

munky : never had issue with p.b. torrents before but i dont save them... i just open them. if you choose to 'open' the download does it show mime type of 'application/x-bittorent' ? And does it return the same extensionless filename if you try from desktop?