I've got a network printer installed on a mac, and you can see it fine in the system preferences print area. It shows as online too.
But, when you go to mail.app for instance (or any app) that printer does not show in the print dialogue. You can click add printer and it installs it again, but once installed it still does not show in the app print window. The printer shows again in the System Preferences -> print area, but not when you go to print from an app.