Welcome to the forum!
It may be a resolution issue. That TV is 720P, correct? Do you know if it can convert 1080 inputs to 720? If not, double check your video source and what resolution it is outputting. Also, the HDMI-to-DVI adapter might be messing up the Pioneer's ability to auto detect your TV's resolution - so, you might try setting the output resolution to 720P. Check out page 65 of the Pioneer owner's manual for how to set the output resolution.