2 wordpress blogs with 1 users table and 1 login

I have been trying to achieve that and I did without the 1 login part

I fallowed this post/tutorial , but no matter what I do I can not get it to login ones for both websites.

My set up is sitename.com/wordpress1/ and sitename.com/wordpress2/(in this one I have BuddyPress installation)

The shared user table work – I can register from wordpress1 site and login with the same username on wordpress2 without any problems, but I need to login for every site separately.

I can see that after I login in the two websites they create 2 different cookies for each:

name: wordpress_38f490d1cc4aa19b4d792ab9d875aaeb
name: wordpress_logged_in_38f490d1cc4aa19b4d792ab9d875aaeb

name: wordpress_8c8848dc05bf5a0a44af5ccc0204cd82
name: wordpress_logged_in_8c8848dc05bf5a0a44af5ccc0204cd82

host: sitename.com //for all of the above.

My understanding is that the two should create only one and use it across.

What do you thing the problem could be? Am I missing something in the settings? Could the problem be in my HOST provider? What about the .htaccess?

Any ideas what I am doing wrong?

EDIT:
From here I read this:

If you plan on creating sites that are strongly interconnected, that share data, or share users, then a multisite network might not be the best solution.

So I chose to use multiple installations instead…