Prints differently than the display
 

I have a large (18mb) dense worksheet, of which I print the first tab which
is full of graphs. On set of graphs displays correctly on screen, but when I
print, these graphs' lines are slightly off (small but noticeable amounts).
It was printing correctly before on earlier drafts of the document. This
happens if I print or print to pdf.
To troubleshoot I tried using different printers and installing different
printer drivers. I tried changing the print processor from RAW to EMF. No
luck. Any other suggestions?
Thanks