We have an internal web application. When the users logon to it internally works like a charm without asking their credentials. 15 users are using this application.
When these users work from home > connect via VPN and go to the http://webapp the dialog box pops up asking for their logon credentials. This is only happening with few clients out of 15. Their AD passwords are cached on their laptops so they should not receive this pop-up again. Plus even if they enter their credentials it does not let them in. Nothing is logged on the web server IIS7 logs either and nothing in the firewall logs either.
When they come to office all works fine without a logon dialog box pop-up.