Hmm, I don't have my DVX with me right now but if I remember correctly, go to menu, hit scene file settings, scroll down to where it says "Progressive," and from there you can switch it between "0ff" (60i), "30p," "24p," and "24p Advance." You can also use the Scene File Dial on the back of the camera to switch it between these.
Have fun with your new DVX!