[Judy Ranelli]"I import into my video app at 720x540."
The resolution of NTSC DV is 720x480 (D1 is 720x486).
If you're using 720x540 PNGs then you want to make sure that they do not use pixel aspect ratio correction in Photoshop.
When you bring your Square Pixel 720x540 image into an NLE you will then need to fit it to the Sequence/Composition/Timeline's NTSC resolution, in effect squashing your 720x540 image down to 720x480 and giving it the proper pixel aspect ratio to be correctly interpreted on a standard NTSC device.
Most programs have a function to fit footage to the correct resolution.
Darby Edelen DVD Menu Artist Left Coast Digital Aptos, CA