I used to play the videos from my iPod touch, but I gave it to my wife to use. So I've put the videos on an SD card. They are playing, but the picture is lagging and very slow. The audio is fine, but the video is too slow too watch. My SDHC card is Class 4. Do I need a faster card? Or is there a particular format the video files need to be? Any help would be appreciated.

I too have noticed this with my 710BT; the same video on my iPhone works fine, but moved to a SD card is very laggy. I suspect this is just the nature of the device and not just isolated to your setup.