Administrators can't access EasyBlog

I recently installed the component for a client. Everything was working just fine. Yesterday, they called me to inform that whenever they tried to access the blog to create a post the "You are not authorised to view this resource." message appeared. I tried to check the permissions but if I go to Components-EasyBlog-Options, the very same message shows up.

What can I do to solve this problem?
Thanks in advance