Just noticed this on the UK site.
If I go to http://careers.stackoverflow.com/uk/jobs/location/london, I see jobs for London, UK.
If I click the Company Pages tab...
my location context has been changed to London, Ontario...
Fixed. Thanks for letting us know.
Problem was: it worked on http://careers.stackoverflow.com/jobs/location/london but not on http://careers.stackoverflow.com/uk/jobs/location/london. So "/uk" was the troublemaker ... some url parsing didn't account for those extra 3 characters, and the location became "on/london" after clicking on the tab. :/
Now the real question of course is: why are there no developer jobs in London, Ontario?