Error – "Unknown login key"

Hello,

I use this plugin on several projects and so far I have had no problems. Today a client comes to me highlight a problem which is as follows :

The domain name is http://yoga-plateforme.fr and redirects http://lemondeduyoga.org.
When I connect to the back-office http://lemondeduyoga.org/wp-admin I am redirected to http://yoga-plateforme.fr/wp-admin normally but when I try to view the site http:/ / lemondeduyoga.org he puts “Unknown login key”.
Screenshot of problem : http://tinypic.com/r/293ivjm/6

Any idea anyone? Much appreciated!
Alex

PS : Sorry for my bad English 🙂

http://ww.wp.xz.cn/extend/plugins/wordpress-mu-domain-mapping/