Is password problem a MobileMe problem?

when I try to login to MobileMe I can sort of, but only get "there was a problem with the sync operation .mac login failed". It works from another user account, but I notice that (with both users) the login preference pane keeps changing my password. Is this a MobileMe problem or something to do with my computer? Previously I deleted all the dotmac plist files and it synced perfectly, but later in the day stopped working again. Any idea on the password issue? Is this the problem? It is correct in my keychain. Seems like I might need to delete a password plist file? I don't know. otherwise MobileMe email and ipod syncing works perfectly - just can't sync contacts and calendar on my macbook

 

thanks for making a suggestion but no luck there - I am on tiger .mac preference pane by the way. And if Apple don't make a mobileme updater available for Tiger my love affair with apple will be coming to an end I think!