it would help a lot of you would tell us what Print plug-in you are
using. If things don't work, the reason might be that you are using the
old gimp-print plug-in, while you should nowadays be using the GIMP
plug-in that comes with gutenprint 5.0.
If you have questions regarding the gutenprint plug-in, please ask them
on the gutenprint mailing-list.
Gimp-user mailing list