Domain Mapping issue : url are displayed like -> http://mappeddomain.com/mysitename

Hello,

Here's my configuration :
WPmu : 4.0
Domain Mapping : 4.2.0.1
Sunrise.php is in the wp-content/ folder and activated in wp-config

I'm experiencing a an issue with the domain mapping.

When I copy a new website, assign it a domain, all URLs in the website are displayed this way :
http://mappeddomain.com/mysitename
http://mappeddomain.com/mysitename/contact

When I'd like it to be displayed this way :
http://mappeddomain.com/
http://mappeddomain.com/contact

I found this topic with the same problem : https://premium.wpmudev.org/forums/topic/domain-mapping-issue-2
But resinstalling didn't help me.

Thanks a lot