chesscharly,
Error 2221 - The user name could not be found.
Looks like you uses account display name (full name in terms of net user) instead of account name (user name in terms of net user). Try to remember account name.
If nothing helps, please send a problem report (Help -> Report a Problem). Maybe we can find usefull information in log files.
Update:
It is possible to use internal windows tools via prlctl exec. For example to get list of users use
prlctl exec "vm-name-or-uid" net user
To get information about user account
prlctl exec "vm-name-or-uid" net user administrator
Thanks.
Last edited: Jan 27, 2013