Username validation for LDAP authentication

It has been reported from one of our customers that when logging in with DOMAINNAME/UserName, the user is authenticated, but not authorized. However, when logging in with DOMAINNAME\UserName, the user is both authenticated and authorized. Of course, the user should not be authenticated when using the forward-slash. Is this a known bug? Frank :)
Aug 22, 2006 16:50
* You are NOT allowed to include any hyperlinks in the post because your account hasn't associated to your company. User profile should be updated.