I don't know. This is as far as I can gather, still a one source story.
It's from AFP, and everyone else is just using this source.
Perhaps they don't think a single source story citing anonynous Iraqu officials is solid enough?
I don't have Fox, so I don't know the standards they tend to follow.
Al Z-whateverhisnameis probably just told 4 stooges they'd get virgins if they took the fall for him.
I believe this is the translation from French.
"4 people linked to the execution of businessman Berg, body found 10 days ago in baghdad, have been arrested, confirmed tuesday by AFP a highly regarded Iraqi source. Asked if more than 1 person had been arrested he replied yes 4.
Then it talks about the execution distributed through internet and the source then continues to say that great progress has been made."