GNOME Printing problems

[Felipe Alfaro Solana]

Hi,

I've set up a machine with Ubuntu Dapper 6.06 LTS. I've also set up an
additional Linux machine running CUPS configured with and sharing an
HP LaserJet 4050 printer with 4 trays, A4 as default paper size, and
using the PostScript driver.

Once logged into Ubuntu, I can see the exported printers but the print
dialog from any GNOME application will show US Letter as the default
paper size and won't allow me to change the tray since the source
media tray dropdown appears grayed out.

What is extremely curious is that OpenOffice.org, KDE applications,
KPrinter and Mac OS X allow me to choose to print to any of the 4
trays and A4 appears as the default paper size.

Any idea on what is happing here?
Thank you very much.