In functioning network, cups client can't see cups server

[Rainer Schuermann]

Setup:

Gentoo Server ("fitpc") running cups 1.4.1 which controls three remote printers (LPD...)

Up to eight clients, running various colours of Linux (Gentoo, Sabayon, Puppy) and various generations of cups (1.3.11, 1.4.1, 1.4.2) working flawlessly with that server. Also occasional guests with Linux and Apple machines have no issues.

...except one machine ("augeatur", running fully up-to-date Sabayon 64)) that refuses to see the server. I have tried upgrading and downgrading cups versions (all of the above), I have edited cupsd.conf  (present configuration here: http://paste/pocoo.org/show/214253), even copied it over from machines that have no issues. Still, the printer list remains empty.
The browser in augeatur shows the printers in http://fitpc:631, so there are (as far as I can see) no network issues.

Any idea what is wrong here? What other information should I post?

Thanks,
Rainer