IE not saving asp.net authentication token / cookies

Question

I have an asp.net site. Its a mixture of web forms and MVC2.

I have this on 2 different servers which I get to via different urls.

On one server authentication works fine via all browsers (IE 8, FF 3.6, Chrome)

On the other IE 8 fails, it doesn't send back the cookie on the request to the page after authenticating.

Using Fiddler I have seen that both sites attempt to set the cookie, in the response from the login page.

Response Header I see from both servers Set-Cookie: DemandLaunch=CCA4...E79C2D1; path=/; HttpOnly

Both sites are in the internet zone of IE.

I'm at a loose for what to check now.

I also have a page that sets a cookie via c# code and that cookie fails in IE as well.

The IE issue is not on a single computer either. I see this failure on 4 different computers Internet Explorer.

My urls which I should have included were:

beta.[site].com - works

beta_[company].[site].com - fails

Answer 1

Check the name of the server. It shouldn't have an Underscore in its name.

If that doesn't help, you should try these out...

http://blogs.msdn.com/b/rahulso/archive/2007/01/17/troubleshooting-cookies-a-case-study.aspx

http://aspalliance.com/1182