On your side, the only thing you can do is to add the software to the exclusion list in the Firewall. Go to Start > Control panel > System and Security > Windows Firewall > Allow a program in firewall (left side). Select the software add it to Firewall, then try to register it again. If it gives you the same error, then there's something wrong with the serial number and the developers have to be contacted to obtain an official answers and a solution to this issue.
They say there is 24/7 support which means you should overcome this easily and fast: http://www.magicuneraser.com/support.php