Sort of bringing this back to the original question: I have heard "all mucked up" used to describe something that is messed up, but not "muckled up".

When I was a kid, the term "muckle" was used in the sense of necking - as in energetic kissing. When 2 kids at a high school party retreated to a corner to make out, they were said to be muckling. I don't believe this usage ever attained widespread acceptance, and as such behavior is rare these days at my office, I don't have much occasion to use it.