Won't print to size from Indesign

Hi,

When I print an A3 page it doesn't print A3, I have spent hours and hours reading and changing settings but it still doesn't work.

I have a piece of artwork with a 12mm white border, I press print and the end result has 3mm border to the left and a 15mm bleed to the top and to the right - it is way off!

Does anybody have any ideas?

(It's a brand new Epson printer, using Indesign CS4, new Mac. It prints fine from Acrobat)

Many thanks

t