Okay - Who knows how to use "poster"?

And I don't mean the syntax - thats in the man-page.
I mean this: I use a gimp-generated eps-file and fire it through poster -
and what do I get ? A seemingly empty file - not by size - there is the
expected contents concerning the filesize - but the file is plain white on
print and upon looking at it. I used lpr for printing, then I tried with
with kprinter, then gimp - all I get to see is a plain white page.

I didn't find that kind of error documented anywhere so far. the files are 4
times the original file by size - which I expect as I wanted to print an A4
picture on 4 A4 pages to get an A2 poster.

what could be reasons that things fail like that?