Bug#418974: Something similar seen here...

[Tim Day]

I was adding a printer to my system (first time it's had a local
printer, first time I've added a printer under Etch; I'd previously,
under Sarge, successfully added a remote SMB printer on a windows
machine).  System was successfully upgraded Sarge->stable Etch recently
following release notes' instructions.

I opened Gnome Desktop->Admin->Printing.
My printer (Samsung ML-2510, USB) was detected, there was no driver
listed; I attempted to add the appropriate downloaded .ppd file from
linux printing site but nothing seemed to change in the list.  I tried
repeating this a few times but apart from it complaining the ppd now
already existed in /usr/share/cups/model, it didn't seem to be
successfully putting anything in /etc/cups/ppd or
updating /etc/cups/printers.conf as might be expected.
Then I looked in /var/log/cups/error_log and there were a bunch of
  cupsdAuthorize: Local authentication certificate not found!
messages.

Then I discovered I could just point a browser at http://localhost:631
and set it all up that way.  No problems getting things working that way
(apart from finding I needed to install some foomatic packages,
including the one which includes all the ppds) and I'm now printing from
all apps just fine.

Tim