If lower baud rates did not help, I still suspect either that your connection has a floating reference, meaning not wired correctly to GND, Tx, RX, especially the GND. If the Rx is floating without a reference you'll see such garbage. Disconnect the cable, insert a pin into the socket's GND socket and, with a ohmmeter, measure the resistance from the DealExtreme serial interface cable's white wire to the pin in the socket's GND socket, checking for a broken wire or poor connection. It should be zero ohms. Test the other leads also - but I suspect the ground reference the most.
The DealExtreme cable's white wire should be connected to the camera's Ground/Common. Normally, the common is on pin 3. The square pad indicates pin 1. The Tx lead, which should be the DealExtreme cable's green wire, should normally be connected to the camera's pin 4 and the DealExtreme cable's blue wire, should normally be connected to the camera's pin 3. The camera's pin 1, the one with the square pad, should have no connection.
Of course, your DealExtreme serial interface cable could simply be defective.