You probably have an orphaned com port that is conflicting with COM4. You will need to change the com port of the FlexControl to a very high port (like COM45) so there are not any conflicts. If you do not know how to do this, please submit a support ticket via our HelpDesk (http://helpdesk.flexradio.com) so we can assign you a case number. For details on how to submit a HelpDesk support ticket, please refer to the following URL: http://support.flexradio.com/ Once the support ticket is submitted, a support engineer will be in contact so we can work on the issue. Make sure to include your radio's serial number.