I have run acrossed an anomaly in ID CS. I have an EPS that I have applied a drop shadow to. The EPS was created with FH10 and imported into ID. The background is none or transparent. The only ink is 100% black. If I have seperation preview off and print to a PostScript file (then make a PDF with distiller), the frame has the drop shadow.

If I turn seperation preview (overprint preview) on and then print to a PS file (then make a PDF with distiller), the EPS graphics in the frame have the drop shadow (which is what I want). Why is the preview effecting output on this matter? The same thing happens if I send it straight to a PostScript printer.