Setting default printer under GNOME
The printer configuration utility under System Settings in the GNOME desktop environment does not allow non-root users to set a default printer, there is a second configuration utility that must be used to do this as a normal user. You can either run the utility from the command line by running "system-config-printer" or you can click the Settings icon in the top right corner of your screen and select "Printers" under "Attached Devices" in the drop down menu. File:Cups util1.png From here right click the printer you want and select "Set As Default"
This problem affects GNOME and GNOME Classic but does not affect Unity or KDE.