How does one print on custom-sized paper with no margins in Ilustrator CS2?

I'm trying to print thank-you notes on 5.5 x 8.5 greeting card paper, using an Illustrator document the same size. The 'Custom' Size option under Media in the Print dialog box was greyed out, so I made a custom paper size with no margins in the Page Setup dialog box, and these dimensions showed up in the width and height boxes underneath 'Defined by Driver'. When I tried to print this, however, a half inch of the graphics were cut off on the bottom. Upon looking in the 'Summary' menu on the Print dialog, I found that it listed the paper size as 5 x 8. I made a new paper size using the same dimensions just in case, but the Summary then listed the dimensions as 6 x 9. Does anyone know what I'm doing incorrectly, and if/how I can fix it?