I cannot edit MediaWiki:Sidebar. The page Special:ListUsers/bureaucrat shows my user ID as both Bureaucrat and Administrator. Even so, when I go to MediaWiki:Sidebar I get no edit button. When I go to MediaWiki:Sidebar&action=edit I get a blank page. Finally, using ?title=MediaWiki:Sidebar&action=edit gives me the "View source" version rather than the Edit version, leading me to believe the system doesn't recognize my rights to edit this. It's unclear to me why.
Logging in as the WikiSysop produces the same results (i.e. cannot edit the Sidebar).
I'm not sure where to look next and some advice would be greatly appreciated.