Hi John,
I had the same problem with XP Pro, the user name and password were identical to that of the user on SME 5.6 but still you had to re-enter the password to get onto the server, never found out why and in the end I just renamed the existing user to something like username_old and then created a new user with the original name and password and Hey Presto got on to the server resources no problem! Lef tit like this for a few days then copied all the original user's docs, favourites etc and pasted them into the new user and finally deleted the old user. I wish I could find out why I had to do this. I have 3 XP machines connected and I never had the problem on the other two!
I Hope this helps.
Regards,
Del