KaraokI Reactivation issues
Make sure you have windows updates disabled as this can mess around with the security files causing a reactivation issue.
Do NOT run registry cleaners, antivirus sweeps etc as this can be the cause as well.
Also please make sure you have downloaded and installed the latest Karaoki update which should also help to avoid this issue in the future: http://pcdj.com/index.php/support/karaoki_support/