Odd behaviour with Membership plugin

Hi - I've installed and am using the excellent Membership plugin on rfpmix.info

However, I've noticed two very odd behaviours depending on whether a user is logged in or out. Let me explain. rfpmix is a site that enables people to draft request for proposal documents, online. It does this through the use of some form-based magic. To create a post, a user has to have registered and be logged on. Draft RFPs (which are posts) created by the site are automatically marked as private posts which only the user who created them can see, i.e., neither other logged-in users nor the general public can see them.

However, and this is the first odd behaviour, if a user who is logged in and who has created a draft RFP clicks on the "Blog" item in the top of the screen navigation, AND THEN clicks in the blog category listing that appears within the list of blog posts that follows, the resulting category archive for that Blog category will also show the private RFP that that user has created, even though it's from a different category. You will only be able to emulate this if you register as a user, create a draft RFP, and then do what I've outlined above. Barry, anyone, could you please take a look this and let me know what might be causing it? I do think it's somehow related to the Membership plugin because I have another site with the same theme but without the Membership plugin where this problem is not replicated.

The second odd behaviour is that, when either a member of the public (ie not logged in person) or a logged in (non admin) user clicks on the "Blog" link at the top of the page, the navigation menu disappears. Again, I think this is related to the Membership plugin because I have another site with the same theme but without the Membership plugin where this problem is not replicated.

Could someone please help with these issues?

Many thanks in advance.

Best regards
Richard