Attendees can hear the presenter but cannot see the video of the presenter.
Reason
The primary reason for this error is that Flash on MacBooks does not correctly detect the built-in camera as the default camera.
Solution
To resolve this problem, please perform the following steps:
1. Right click on the A/V window and select Settings.... 
2, In the Adobe Flash Player Settings dialog box that appears, click the camera icon.
3. In the list of cameras that appears, select the correct camera from the drop-down menu.
Note:
Macromedia does not label it as an iSight
camera but as USB Video Class Video.
