We use Exchange2K with about 1200 users. All desktops are W2K. One particular user floats within her department and uses Outlook Web Access on other PCs to get her mail. She does not login as her self on any PC. She opens IE 5.5/6 and connects to OWA then uses her user name and password to get to her mailbox. When the login takes her to the mailbox, she now gets a second login screen. If she logs into it, the screen goes away and the mailbox is fine. If she cancels past the login screen, it says login failed but the mailbix is still fine and functional. There are hundreds of other users who do the same process but she is the only one who gets the second login screen.
What is causing the second screen to appear?