I password-protected some podcasts I made for my students, using a Windows Server 2003 machine with IIS.

Almost all students have no problems accessing the podcasts, whether on Mac or on PC, whether with iTunes or other software. They are prompted for a password and enter their university creditentials (I connected the folders to the university's logon system using Integrated Windows Authentication).

The problem is that two of my students get a weird behaviour from their iTunes. It just doesn't prompt them for a password. Next to the episodes they try to download, an exclamation mark appears saying that the podcast is protected, but there doesn't seem to be a way of having iTunes ask for their usernames/passwords.

Can anyone help me with that? I've been looking around their laptops for clues, but everything seems to be perfectly normal and I can't figure out what's different in their case (it works fine on my own MacBook Pro).

Thanks a lot,