* Yahoo! Messenger might have the wrong camera selected. Follow the steps below to change your camera source.
1. Click “Messenger”
2. Click “My Webcam.
3. Click “Messenger” again.
4. Select “Preferences.”
5. Click “Webcam.”
6. Click “Camera Source.”
7. Click the pull-down menu and select the camera you want to use.
8. Click “OK.”
for more info click onto the link:
Webcam Display issue while Accessing through any messenger for Video Chat | Techyv.com