Cannot grant capabilities to administrator

I recently installed the members plugin which seems to be doing an amazing job at restricting my content to various roles. Howerver, the admin role has not been granted accesss to edit files, update or install plugins, update or install thems, etc. When I check on the box to grant the admin these permissions and save, the page just refreshes with these boxes unchecked. So I cannot grant these permissions.
As an admin I cannot do updates or installations on my site now. Kindly advice on how to fix this.