Hey Thomas,
First, thanks for your answer.
Second, here is what’s wired. If I use the SharePoint admin console in Administrative Tools, I can add users from the Domain and give them for instance, read rights to a site, but it will not let that user access the site.
If I try to add users a Domain user from within the Site, it will not let me do it. If I log on the SharePoint server with that user name, then I am able to add the user and then the user can access the site. Does this make any sense?