I tried what you suggested but the problem still remains.  It is very intermittent if a single user tries to log in (myself) all day log doing development work, that user (myself) has no problem logging in and out.  If I try to add users to this equation, I get the errors and unable to login.  Two common situations arise, first pass through authentication seems to always work, second situation is that it appears that once a new user logs in other logins are not able to login any longer, if they are not using pass through authentication, or if a user logs in not using pass through authentication then logs off and trys to log back in it also fails.

Any help is appreciated.

Thanks.

Derek

Hello Derek,
Just out of curiousity, are you using IE only in this situation, or are a variety of browsers being employed?  I ask because I encountered an intermittent authentication issue recently and it turns out the problem was IIS based, not DNN based.  Essentially, the user could not authenticate against the domain when using IE (any version).  It appears that when IE was authenticating, it was authenticating against Kerberos, which my domain is not set up for.  There's an MS article on it here:
http://support.microsoft.com/kb/215383

Here's the command I had to run in order to make this change.  BE CAREFUL!  This will modify your IIS Metabase, and if not done correctly, can seriously hose your environment.
C:\Inetpub\AdminScripts>cscript adsutil.vbs set w3svc/NTAuthenticationProviders "NTLM"

Hopefully this helps.

-- Scott Allender
http://www.scottallender.com