I use Outlook (2003 SP2) to collect mail from a couple of POP3
accounts - Yahoo! and my ISP account. All has been running smoothly for
months...until now.

Although Username and Pass are 'remembered' (and are correct), every
time Outlook performs a send/receive it requests username and password.
Ticking 'save this password...' on the pop-up makes no difference. The
user and pass are prefilled on this pop-up, but the annoying window
often appears more than once per send/receive.

There's no other resource accessing the same accounts, the user/pass
are correct, and amending the registry as per this Microsoft Knowledge
Base made no difference (http://support.microsoft.com/?id=290684).

Any advice gratefully received...