Problem after changing domain

I set up a site using a sub-domain. Then after it was finished i pointed the normal URL to the new drupal site and got a white page.
I then cleared the cache and it works well if not logged in.

Now I tried to log in as Admin and as soon as I log in I get the white page again (depends on the template with some I get a white page wwith a skip to content Link).

If I use the old subdoain ( all works perfectly. But as soon as I get rid of the “drupal.” and only call the domain it wont work even they point to the same drupal directory.

I tried clearing the cache again – nothing.

I tried running update.php – he tells me no update necssesary.

What is the problem? What do I need to do?

Drupal version: