Can't login at main screen of Mac Pro. Only thing to click is cancel., software was updating at time don't know why password won't work.
Welcome to the Apple Support Communities
If you don't remember your password, see "Resetting your original administrator account password" > http://support.apple.com/kb/HT1274
If you are using OS X Lion or OS X Mountain Lion, see > http://discussions.apple.com/docs/DOC-4101
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