Impossible direct access to a dashboard from the admin

Hi,
Could you explain, please how to solve this problem?
A website has 3 admins-2 are the owners of the website and I help them with the design.All 3 of us have a proper admin accounts but only I’m able to log into dashboard directly. The other two will go to http://www.domain.com/wp-admin and will put the right login details. Then they will see a message -You do not have sufficient permissions to access this page.Actually they are logged in. if they go directly to http://www.domain.com/, they will see the home page and the tool bar with the dashboard’s links. It is annoying, but atleast they are in.
Once they are in, they can’t go to the dashboard immediately.They have to go the themes, menu or any other link and THEN if the click on a dashboard will be able to go to the actual dashboard. Which is irritating too.
FYI WP is a fresh installation 3.6 but with the old config.php(from 3.5.2)
Only one plugin-qtTranslate, only, because it has a line in a header.php and if the plugin is off will show an error when reach the website.
The theme is twenty twelve.Nothing else fancy or complicate.
I have read all topics with the “You do not have sufficient permissions to access this page” problem and I followed all scenarios but I didn’t succeed.
Somebody with wish to help, please?
Thank you!