What method are you using to print from Filemaker?
Are you choosing print from the file menu or clicking a butto that uses a script.
If you are choosing print from the filemenu, you should be able to use Print Setup to specify media. If you are using a script, you may need to update the print setup and/or print steps in the script.
Actually, I'm using print from the FM menu - but can't choose plain paper... it's grayed out
FMP 9 did have some issues with some printers though I don't recall any Epson printers with issues...
Things you can try:
Trash filemaker preferences and see if that makes a difference.
Don't recall if Mac printer drivers have a preferences file, but if so, trash it.
Re-install FM9 and re-install the printer software.
Download Filemaker 11 free trial software and see if it works.