Hi,
Are you trying their Name and password on your account (and not in Michigan) and in other Users Accounts ?
Or are you just trying their name on their computer but also in different User Accounts ?
If it is on their Computer does the info in the Keychain (Applications/Utilities KeyChain Access) match what they think it is ?
See also
this Users Tip about whether it matches the Registration site.
If on your Computer you may need to talk them through accessing the Keychain info.
You may need to use
this site for @Mac.com info if they use it as an Apple ID as well
If it is still used with a paid-for MobileMe account you should be able to Login there as a check.
8:48 PM Friday; April 9, 2010
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"