It's a long shot, but have a look at the properties for your printer (Go into Control Panel --> Printers and Faxes --> Right click on the printer and choose "Properties"). Click on the "Advanced" tab and you'll see a "Seperator page" button in the bottom right corner. Click it, and make sure the resulting box is totally empty.
After that; the best bet is to look through the "printing preferences" - to get to them, click the "General" tab of your printer property screen and click the "Printing Preferences" button - you'll need to look through all these screens yourself as I'm afraid I don't have the same printer as you so can't tell where the option for "seperator page" might be.
Good luck with the diagnosing!