Thanks for the response. I've had a play and it's a problem with macam which occurs when the macam component is installed but no USB camera is plugged in - happens in other apps too. Works great with a USB camera attached and with my iSight.
Really great - though config button crashes for me - may be the fault of the macam driver though. Is there a way to download all of source at once? Seems can only browse/download individual files.