Printer auto-detection and scanning no longer works

[John O'Hagan <johnohagan@iprimus.com.au>]

Hi,

This post has already appeared a couple of days ago on debian-kde, so 
apologies to those who've already read it... 

Until recently, on my up-to date testing laptop, KDE would automatically show 
me all available network printers under "Print System" and in the Printer 
drop-down menu under File -> Print in KDE apps.

Lately, though, I must manually add any network printers. To use the "Scan" 
feature of "Add Printer", I must change the subnet used from 127.0.0.* to, 
say, 192.168.1.* for it to succeed. This is a pain as I move around a lot.

My cupsd.conf has the line: 

Listen localhost:631

Browsing is on and BrowseAllow is set to All.

I've tried various other settings, each of which either renders CUPS 
inoperable or makes the scan exhaustive within the 127.* subnet, but doesn't 
restore the former automatic behaviour.

Purging and reinstalling CUPS makes no difference.
 
To be honest, I'm not sure how this is supposed to work, or whether the 
problem is with KDE, CUPS or networking. 

Anyone else seen this or know how to fix it?

Thanks,

John