I have the same problem. I'm using Outlook 2003 from Office
Professional 2003 on a Vista Ultimate system. My ISP is Att.Yahoo and
is a paid subscription.
I just recently upgraded from Office 2002 on an XP system to Office
2003 and a Vista system.
I am very happy with Outlook 2003, especially compared to Outlook
2002. This is the only niggling problem I am having with the program
and it is not a serious one. I stlll download my messages from my
server without interruption and just have to close this Enter Network
Password request window after each download. However, if there is a
way to eliminate this repeated request with each download I would do
so.