When participants in your Mikogo session only see a black screen instead of your screen transmission, it's possible that your personal firewall, such as Webroot, is blocking the Mikogo transmission.
In order to allow Mikogo desktop sharing while your Webroot "Secure anywhere" is active, please follow these steps.
1. Open the Webroot menu by right clicking on the "Webroot" icon on your task bar and selecting "View Status"
2. Click on the cogwheel next to "PC Security".
3. Under "Shields and Firewall" click on "View Active Connections"
4. Choose Mikogo from the process list and set it to "Allow".
Please check if the IP-Adress on the bottom is allowed, too.
5. Close the previous window and click on the cogwheel of the "Identity Protection" in the webroot menu.
6. Set the "Mikogo-host.exe" to "protect".
7. The screen will now be displayed normally.