Indesign prints same file differently on separate machines?

I have a question and hoping somebody will be able to help out.

We have indesign CS5.5, on both machines, and both machines are on 10.6.8. One machine will print out correctly, the other will print out the same document a lot darker, for instance flat colours come out miles apart?

Could anyone shine some light on why this is happening?

Cheers

Andy