Problem with new users being blocked from content after signup

I'm having a major issue with new users being blocked from seeing any site content after coming back from 2checkout after the initial signup. I'm not sure how this is happening since I DO NOT have any rules set up to block content at any level on any page. New members are not displaying any membership level after signup in the admin area under "All Members" at all.

I have enabled the global instant notifications url pointing to http://mysite.com/paymentreturn/twocheckout

Still nothing. Any ideas on how to fix this?

This is a spin-off from this post http://goo.gl/PNRM5W