Answer 3
This may be more of a client-side problem than an asp.net problem.
Since the problem happens for some clients and not others, I wonder if this might be a case of the client saving the credentials. Sometime when a users is prompted for credentials, there is the option to "save this password" and that could play a part in this type of problem. Which version of IE is seeing the problem? IE 6? IE 7?
Typically windows integrated authentication shouldn't prompt a client for credentials if that client is on a workstation that is joined to the same (or trusted) domain. You may want to check to see which internet zone IE thinks the address is in. Which zone shows up in IE when the problem is reproduced?
Ideally you'll want the website to be set in IE's "local intranet" zone. Also ideally the IE client should have the default setting of "Automatic logon only in Intranet Zone."
For IE7 or IE8 you might try clearing passwords to see if that makes any difference.
Internet Explorer 8
To remove a stored password or other stored information in Internet Explorer 8:
1.From the Tools menu, select Internet Options.
2.On the General tab, under "Browsing history", click Delete... .
3.Check the item(s) you want to delete:
?Temporary Internet files (copies of web pages, images, and media that are saved for faster viewing)
?Cookies
?History (the lists of web sites you have visited)
?Form data (saved information you have typed into forms)
?Passwords
?InPrivate Filtering data (saved data used by InPrivate Filtering to detect where web sites may be automatically sharing details about your visit)
To delete everything, uncheck Preserve Favorites website data and check all the other options.
4.Click Delete.
Internet Explorer 7
To remove a stored password or other stored information in Internet Explorer 7:
1.From the Tools menu, select Internet Options.
2.On the General tab, under Browsing history, click Delete... . You now have several options:
?To delete temporary Internet files (copies of web pages, images, and media that are saved for faster viewing), click Delete files... .
?To delete cookies, click Delete cookies... .
?To delete the history (the lists of web sites you have visited), click Delete history... .
?To delete form data (saved information that you have typed into forms), click Delete forms... .
?To delete passwords, click Delete passwords... .
?To delete all of the above, click Delete all... .
3.Click OK twice.
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For IE6 you might experiment with http://support.microsoft.com/kb/229940 - How to disable Internet Explorer password caching. "When you try to view a Web site that is protected with a password, you are prompted to type your security credentials in the Enter Network Password dialog box. If you click to select the Save this password in your password list check box in this dialog box, the computer saves your password so that you do not have to type the password again when you try to use the same document. This behavior is known as password caching."
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