Hi Klaus,
So you are working with the code from svn right?
Setting AllowLoginWithUsernameWhenSiteSettingIsUseEmailForLogin = true should have fixed that. Did you put it in user.config? Remember it won't pick up changes to user.config automatically, you need to touch web.config by type a space and save so it can reload all settings.
Another thing you can try is go into the mp_Sites table and set UseEmailForLogin to 0 or false
I will add a check in the code so it doesn't enforce email login when using ldap auth even if UseEmailForLogin is true.
Hope it helps,
Joe