Nesting and Aspect Ratios

It's been awhile since anything's made my head spin like this.

The video I shot in 720 x 480 needs to be exported as an FLV (I export from FCP then convert in Sorenson) to fit into a player that is 640 x 432 (square pixels) without distortion, meaning with pillars.

I tried nesting the sequence in FCP, and it gave me great pillars, but upon rendering the video was distorted with wavy lines (I set the sequence exactly the same as the other sequence, but 720 x 432). I tried exporting it 640 x 432 and choosing the "letterbox" option, but it didn't give me the desired pillars. In Sorenson, I tried importing my 640 x 480 file and converting to a 640 x 432 choosing the "letterbox or pillar" option, but it didn't do it.

Wow! Help.

Select "padding on" in Compressor?

Thanks, I'll try this! Luckily, I got around the issue by having our company fix our player to prevent aspect ration distortion.