Default page size in shared printers

[Fabio]

I really can't realize what is happening.
I connect the same eeepc to two different desktops. 
The two desktops have the same version of ubuntu and cups, and 
they share the printer (two different printers but rather similar: an
epson stylus photo 870 and an epson color 1160, both with the
gutenprint-ijs-simplified.5.0 ppd).

Well, what I get is that when I connect the eeepc to the desktop with 
the EC 1160 printer, the autoconfigured printer on the eeepc has the 
correct default page size (A4), whereas when I connect to the desktop 
with the ESP 870 then the printer on the eeepc has letter as default page
size, no matter how I set the default on the cups server on the desktop.

I also tried to remove all "Letter" occurrences in the ppd on the server,
but it is still the same.

All in all, it seems that the client on the eeepc doesn't care about
the server settings on the desktop which serves the ESP 870 but it cares
about the server settings on the other desktop.
As I said, the client is (of course) the same; the servers are different
but with the same OS/kernel/cups. So, what happens?!?

The only thing that change is the network. Should I describe how are
configured the networks?

Thanks

Fabio