In Discus or any printing application, make sure to go to File - Page Setup.
Select Disc Publisher in the Format for: field.
Select CD/DVD in the Paper Size: field.
If you do not select the printer or the paper size it may not print at all, or the application may assume that the page size is 8 1/2" x 11". This would cause the Bravo to print part of the image on one portion of the disc and print the rest on the tray.
If you are printing through Discribe see this article.