Just to add to this. I just want to add that I'm using XFCE and I have the same problem. So it isn't necessarily related to GNOME. Is more likely a GTK problem? I tested it with GIMP, Evince and Firefox. AFAIK they all use the GTK printer dialog.
I added my normal user to the lp group in the hope it might work with version 2.4.15-1 but it didn't. I have reverted to version 2.4.14-1 as well for now.
