Blank Login Page, Domain and Host different providers

Hi guys,

I have a problem with my wordpress login and I think this is because of my setup. My Domain is with another provider than my webhost. So I have blog.example.com redirecting to webXXX.mywebhost.com.

I have setup define(‘WP_SITEURL’, ‘http://blog.example.com’);
define(‘WP_HOME’, ‘http://blog.example.com’); in my config file.

The blog is accessable via http://blog.example.com, but when I try to access admin dashboard via /wp-admin it first redirects to http://blog.example.com/wp-login.php?redirect_to=http%3A%2F%2FwebXXX.mywebhost.com%2Fwp-admin%2F&reauth=1, the login window shows up, but after hitting submit I get redirected to a blank http://blog.example.com/wp-login.php page.

Can anybody help me on this? Have been troubleshooting and googling for 2 hours now, but still no clue, how to change this.

Btw., when I configure and use webXXX.mywebhost.com in wp-config, everything is working fine, so it must be related to the domain change.

Regards,
Daniel