just received my playbook a few days ago.
I tried the camera and video. everything was working fine until today.
I got blank screen with the 5mp camera ( 3mp one is ok ) all the setting widgets are displayed but no image from the cam.
Reboot or restart. You can use the ICON or you can Press and HOLD all at the same time: PowerON button, and both the Vol up and Vol down buttons to force a reboot.