Invalid podcast image

Hi,

I've read several post about the error "The feed does not contain a valid podcast image. Podcast images must be at least 1400 x 1400 pixels." and I my feed already contains the correct image size. I'm still getting the error and cannot submit a new feed. Anything wrong with my feed?

This is my feed url: http://feeds.feedburner.com/AccentureDigitalPodcast