iPhone 4 that it says can't play Expendables 2

I have an iPhone 4. I added my Expendables 2 (iTunes digital copy) to my movie list and tried to sync it. When it got to the Expendables 2 movie I got an error message saying that it can't sync because it cannot play on this iphone. Everything else went on it fine and I have no playing issues with anything else. I'm pretty sure the iphone 4 can play HD video if in fact it is a HD digital copy. Anyone have any ideas why that one in particular won't sync?