Masks created by MaskIt and some other applications appear to cut out the background of the page when viewed in Acrobat 7. This has been confirmed as a problem in Acrobat by Adobe. The issue has been fixed in the 7.0.5 critical update. If these files are printed then the problem is not shown in the print.
To fix this problem users should make sure that the 7.0.5 critical update is installed for Acrobat 7 Professional, Acrobat 7 Standard and Adobe Reader ver 7.