Cannot login from User Login block

I wanted all my users have their profile to username.decoclub.gr and when a visitor (or user) views a page, story etc, e.g. from user aris, the url to be aris.decoclub.gr/page/about

All working great! Subdomain Prerequisites all working (as you can see in subdomain_prerequisites.png).
I changed the automated url alias as you can see url_alias.png and I have the functionality described.

The problem is that I can't login from the user login block, BUT I can login from the www.decoclub.gr/user page!
You can see my login attempt in login_attemp.png and the result in login_result.png. As you can see in browser's url, I have been redirected to my front page without login.

My site has always www in front of the domain. BUT, when I hover over Drupal's links (Administer, Create content, ...) in status bar the url is decoclub.gr/admin and not www.decoclub.gr/admin as it should be.
You can see in file url.png that the cursor is over site's name, the status bar shows decoclub.gr and the url in browser is www.decoclub.gr. If I click I see the correct page.

I tried to remove www from disallowed subdomains but I take a page not found!

Any ideas? I'm so close to have what I wanted!