Printing Opactiy Masks : Adobe illustrator

This is a discussion on Printing Opactiy Masks within the Adobe illustrator forums in Adobe Tools category; I just sent a brochure to the printers and every image I used an opacity mask on did not print at all. The file was created in illustrator then placed into indesign for the layout. I output a postscript pdf from indesign and sent it off. It came back ok with the exception of not printing those images. I cant sit here and except that Adobe would create this design tool and not have the ability to actually print it using any process. Am I doing something wrong?...