VirtualHost _default_:8081 -- mixing * ports and non-* ports with a NameVirtualHost a

Hello,
I installed ispconfig but when i went to http://mydomaine.com:8080 or https://mydomaine:8080 (the same with port 8081), i had an error:

https://domain.fr:8080/

Code:

Internal Server Error

http://domain.fr:8080/

Code:

Bad Request 

http://domain.fr:8081/

Code:

Forbidden
You don't have permission to access / on this server.

https://domaine.fr:8081/

Code:

Erreur SSL

Foreover, when i reloaded apache2, i had this

Code:

root:/etc/apache2/sites-available# /etc/init.d/apache2 restart
Forcing reload of web server (apache2)...[Sat Apr 17 19:57:56 2010] [error] VirtualHost _default_:8081 -- mixing * ports and non-* ports with a NameVirtualHost address is not supported, proceeding with undefined results
[Sat Apr 17 19:57:56 2010] [warn] NameVirtualHost *:8081 has no VirtualHosts
httpd (no pid file) not running
[Sat Apr 17 19:57:56 2010] [error] VirtualHost _default_:8081 -- mixing * ports and non-* ports with a NameVirtualHost address is not supported, proceeding with undefined results
[Sat Apr 17 19:57:56 2010] [warn] NameVirtualHost *:8081 has no VirtualHosts

Have you got any idea?
I searched in this forum but nothing :'(

PS: sorry for my bad english, i am french