Hey Mike, Sorry to jump posts but I think you are on the right track about OnAuthenticateRequest(Object s, EventArgs e) . I noticed this in my Win 2003 event viewer.

Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 10/26/2007 11:51:40 AM
Event time (UTC): 10/26/2007 3:51:40 PM
Event ID: 9c5a24df928c4c378fb5290143a3d281
Event sequence: 5
Event occurrence: 1
Event detail code: 0
 
Application information:
    Application domain: /LM/W3SVC/843418/Root-1-128378874849088719
    Trust level: Full
    Application Virtual Path: /
    Application Path: D:\Webs\RdcDnnIntranet\
    Machine name: RDCMS-INTRANET
 
Process information:
    Process ID: 5612
    Process name: w3wp.exe
    Account name: NT AUTHORITY\NETWORK SERVICE
 
Exception information:
    Exception type: NullReferenceException
    Exception message: Object reference not set to an instance of an object.
 
Request information:
    Request URL: http://rdcms-intranet:8082/WebResource.axd?d=qvGa4hNu2OCbE_Jk2VVTFw2&t=633207389898171851
    Request path: /WebResource.axd
    User host address: 10.1.136.150
    User: 
    Is authenticated: False
    Authentication Type: 
    Thread account name: NT AUTHORITY\NETWORK SERVICE
 
Thread information:
    Thread ID: 1
    Thread account name: NT AUTHORITY\NETWORK SERVICE
    Is impersonating: False
    Stack trace:    at DotNetNuke.Authentication.ActiveDirectory.Configuration.GetConfig()
   at DotNetNuke.Authentication.ActiveDirectory.HttpModules.AuthenticationModule.OnAuthenticateRequest(Object s, EventArgs e)
   at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
 
 
Event code: 4006
Event message: Membership credential verification failed.
Event time: 10/26/2007 11:51:33 AM
Event time (UTC): 10/26/2007 3:51:33 PM
Event ID: 9af5fa795826453ebf7573102471f851
Event sequence: 3
Event occurrence: 1
Event detail code: 0
 
Application information:
    Application domain: /LM/W3SVC/843418/Root-1-128378874849088719
    Trust level: Full
    Application Virtual Path: /
    Application Path: D:\Webs\RdcDnnIntranet\
    Machine name: RDCMS-INTRANET
 
Process information:
    Process ID: 5612
    Process name: w3wp.exe
    Account name: NT AUTHORITY\NETWORK SERVICE
 
Request information:
    Request URL: http://rdcms-intranet:8082/rdc/windowssignin.aspx
    Request path: /rdc/windowssignin.aspx
    User host address: 11.1.1.1
    User: 
    Is authenticated: False
    Authentication Type: 
    Thread account name: NT AUTHORITY\NETWORK SERVICE
 
Name to authenticate: MAIN\MyName