I had the same problem. With me it was caused by installing MSN Messenger.
When I realised I preferred to work with Windows Messenger, the installation
of MSN Messenger had deactivated automatic sign on for Windows Messenger.
Removing/uninstalling MSN messenger did not solve the problem. The only
solution I could find was the 'Restore' function to the point before I
installed MSN Messenger. This will only be practical if you installed MSN
Messenger not too long ago. After restoring to this point, Windows Messenger
signed on automatically.
"Alain Stucki" wrote:
> I have set up several computers with XP and using the Windows Messenger
> works great. All Messengers are set up to start automatically when Windows has
> started. Every computer shows the Messenger icon right next to the
> clock on the task bar but on some installations it doesn't log-in
> automatically. These users have to right-click the icon and click on
> login. Then it works.
>
> Alain
>
>
>> Stay informed about: Automatic Login