Text colour error inside a graphic box

[aaat0519]

I have put a text frame within a graphics frame and when it's printed at the printers the text comes out a bit fuzzy and not pure black. It's as though it's treating the text as part of the graphics frame. It doesn't do this on my Epson Acculaser at home. The printers also use a laser printer but I don't know what it is.

Any ideas?

Thanks.