Normal users can't view posts, only admins can

Hello,

Our membership plugin seems to be acting up. We have set up 2 types of permissions, one is for ‘normal users’ and another is for ‘stranger’.

It used to be working fine. But now our normal users cannot view any post. Once they are logged in, they can see the homepage okay and the headlines of the posts, but when they click on a post they are sent to no-permission page.

We have checked the membership settings and all looks fine. The categories are all ticked (under positive tab) to give permissions for people to see the posts under them.

We have disabled the themes and plugins, but that didn’t work. The posts load fine, when the membership plugin is disabled.

Please can you help?

Many thanks.