I am having the same problem, but I am not on Win 2K3 server. The ghost server is on Win XP.
The command is:
net use g:
\\servername\sharename * /user:servername\username (I am using "servername" because the account is a local account on the servername server.)
Then I get:
"error 2202: the user name or groupname parameter is invalid"
I have tried to change the command in several ways. I've gone onto various websites and am sure that I have the syntax correct for the "/user:" parameter.