error when using mpeg2encode
 

I'm converting JPEG images into MPEG-2 movie files by using the Imagemagick <convert> command to convert the images into yuv format & then encode them into mpeg-2 format using mpeg2encode (from the mpeg2vidcodec-1.2 RPM package)
All of the jpg's convert to yuv fine, but when I try to encode them from yuv into mpeg2, I get an error message on one of the files, it says:

>horizontal_size must be a even (4:2:0 / 4:2:2)

obviously it's complaining about the size of one of the JPEG images, but I don't know exactly what this error means. If anyone has ran into this before, or knows what this means, or how to resolve it ... any clarification would be helpful.