Are you attempting to authorize a Single Use product? Is this a new installation of the software?
I would contact your local Technical Support Team, as this may require a screenshare session.
In the mean-time, I would suggest rebooting the machine, then trying the Authorization process again. Make sure that all ArcGIS products are closed when you attempt to Authorise the product.
If that does not help, you may need to complete a full, clean uninstall and reinstall. Make sure that there are no ArcGIS products open / running when you reinstall the software.
Excelsior.