David82:
The same effect is seen even when using 8AA batteries instead of the pc power supply
The wires from the power supply may be too small to pass sufficient starting current to the motor resulting a brownout of the camera. Particulalry if your AA batterys are in one of those radio shack battery holders, that could be an issue. If the cam could operate at 11v instead of 12v, then a diode in the cam + wire with a big capacitor between the diode and the cam, your problem might be solved. If you can't change any thing, then note the below.
Insanity: doing the same thing over and over again and expecting different results.
Albert Einstein