What am I doing wrong?  My DNN site is an intranet.  I also have an asp application that is a second site.  It has an external authorization mode that will allow you to logon automatically by passing the username via URL parameter called 'ext_uid'.  I can logon as much as I want directly from the IE address bar with a URL like:

http://myothersite.com/logon.asp?ext_uid=myuserid

So I created a page with an IFrame module and the URL is http://myotheriste.com/logon.asp and I created a a querystring parameter called ext_uid and selected Users Username. 

This works perfect for every user one time and one time only.  On further attempts my other app sends an error page that says 'No username was specified by the external authenication'.  Yet I can again put the url string in IE and go right to it with no problem.

Thanks in advance for any help.

Yes.

 Interesting... OK, keep us posted if something isn't working again... :)