I found out that the shortcode is not compatible with shortcode from WP-Members plugin. I removed the shortcode from WP-members and the onlog button from clef worked perfectly. So for the people who has the same problem. The conclusion is that clef and WP-members plugin doesn’t work together. I’m still working on a solution to get a login page with WP-members and clef together in 1 post.
Thanx for the reply lawrence;)