Last modified: 2008-12-15 14:48:55 UTC
To reproduce: attempt to move any page to a valid interlanguage or interwiki prefix. Eg moving [[Foo]] to [[fr:Foo]] or [[wikt:Foo]]. The error message that is produced is [[MediaWiki:Movenotallowed]], intended (AFAIK) for warning users who have been blocked or de-autoconfirmed since the form was loaded. A more specific and informative warning message should be displayed instead.
Confirmed. The content of [[MediaWiki:Movenotallowed]] just tells that the requisites to move the page, but you can have the move right and not be able to move it, by trying to move to an interwiki as comments Happy Melon, or moving to/from an immutable namespace.
Fixed in r44624