Why did Maiden split with Martin Birch?

sknight

Are You Morbid?
I've checked all over the web and couldn't find anything about it. Was it a creative split, or was it simply that Birch no longer wanted to work with them (or the other way around)?

I'm not a big fan of Kevin Shirley. He makes the albums sound too flat and not as dynamic as Maiden is. Dream Theater fans have the same complaint, as well as him messing up the sound on the DVD.