mac client doesn't detect ipp printer

[leonardo canducci]

I'm using cups 1.4.0 from debian sid linux and I have an HP deskjet
 printer connected via USB. This printer is shared and visible: I
ticked "Share printers connected to this system" and "Allow printing
from the Internet" in the web gui.
I can print from linux clients either:
- creating a client.config file in /etc/cups/ (cups-client only)
- configuring a printer with a gui/wizard where cups is installed
In the second case the gnome GUI can detect and configure the printer
specifying the server address.
Since I upgraded to cups 1.4 this IPP printer detection doesn't happen
anymore with mac osx leopard and in some way upgrading cups to 1.4.0
broke printing from it with the old printer profile.
Some time ago I managed to configure the printer on my wife's macbook
using the settings GUI but now I can't. I set IPP protocol and the
server address and it finds no printers. I can manually set the printer
queue but then the printer driver is non optimal (hpijs, the one used
when connecting the printer directly to the mac, is not even presented).
This laptop is connected wirelessly (same as the linux clients) to the
server. It can ping the server and can also print using lp -h in the
console but it's not able to detect the printer with its GUI as all
linux clients can. As expected using an ethernet cable instead of
wireless is no use as well as switching off firewall.

Any hints for troubleshooting this problem?

Thanks