When I'm logged in as admin, the urls are un-aliased ("node/24"). When logged out they appear aliased ("about/us"). It might have something to do with the module admin_menu as suggested in a post over at drupal.org – but applying the recommended patch didn't work for me.
Hope somebody knows a way out? Thank you! t
update: thank you for suggesting to investigate first, if it REALLY is the admin menu – and of course it's not. I switched it off, but same situation. So I guess I'll better do some further 'research' by switching off and on various recently installed modules first…