Windows mail security problem

[#1]

Hi Just set up for first time. Windows Vista Home Premium and Windows mail.  When sending/receiving we often, but not everytime, get a windows security message asking for username and pword. Whatever we enter it fails. We might return later, do send and receive and all will be ok.
Any suggestions?

[#2]

Have you got secure authentication turned on, perchance? Go to Tools - Accounts, then click your account and go to Properties. On the Servers tab, make sure "Log on using Secure Password Authentication" is not ticked.