Can't add site or domain or email

I need to add a new client along with their email, website, etc. I've added the client successfully but, if I then go to add email domain, website or DNS it won't let me. Specifically, it asks for a domain. It gives me a dropdown list of the domains it already knows about but won't let me create a new one. The only one that's different is the add DNS zone wizard, where the dropdown list is empty. I type in the domain name I need and nope, won't accept it; as I tab it it clears the field.
Am I doing something stupid?

 

add the domain under client / domains or disable the domain-module

 

Thanks florian30. I don't remember having to do that in the past, I gues it's a new feature. However, it worked.