There's nothing relevant in the OSM database with name=British Colombia. The relation is spelled correctly.
Comment from dekarl on 26 March 2013 at 10:36
Have you checked for ID collisions? As in the same number for a different object type (node/way/relation). I've got a similar (but less visible) issue where my home is mistaken for a super market >500km away.
Comment from Andy Allan on 26 March 2013 at 16:26
I guess it's either outdated OSM data, or more likely, a mistake in a Natural Earth dataset that they are using. If you zoom in on the BC/Alberta border and check the data layer, you'll see they aren't using the OSM boundary.