We are currently using version 3.0.13 of DotNetNuke with Tam's authentication module and we have run into a very interesting/difficult problem. 

Background:  Business rules dictated that we modify the authentication code to delete roles and pull Active Directory (AD) groups every time a user logs onto the site.  The site works for a while and then all of a sudden stops pulling the group info from AD.  We've deleted a user and then logged in with that user again and the account is created with all the AD info except the group membership.    We also verified the AD connections on the Authentication page and all 3 tests are passed.

We are at a bit of an impasse and would welcome any recommendations.

Thanks,

Chad