Jce editor groups- problems with multi permission

Question

I have Joomla site with JCE editor. I use the JCE groups to create permissions for different users.

I have created few groups and every group is permitted to control one media directory.

I have combined a specific user to two different groups assuming that this user will have the ability to access two different media directories.

But the user can access only one directory and the first one I have gave him.

Can anybody help me to fix this problem,

and what I should do in order to give a specific user access to different directories ?

Thanks!!