Can't login with new user

I created a new user on my modx site. But i can't login with the username and password. The username and password are good, because i don't get an error. If i fill in an other password it gives an error.

But instead of an error the page just refreshes without logging in..

My own account still works.

First, try clearing your browser cache and cookies for the domain.

If that doesn't help, you'll need to go through the process of creating a new user and assigning him to an appropriate user group again. Revo user management is not easy.

This is one of the best sources of information http://bobsguides.com/revolution-permissions.html

Now the menu is gone on my site and when i go to the manager i see a blank page (and i didnt change anything)

i have to say i liked the old modx system much better..