Description of problem:
lp, lpq, kprinter all report that no printers are found. 
The machine next to mine can see all configured printers.

Here are some commands we've tested vi IRC:
#lpstat -r
scheduler is running

#lpstat -s
no system default destination
lpstat: No destinations added.
lpstat: No destinations added.

#tcpdump udp port 631
16:05:19.569772 IP someprintserver.redhat.com.ipp > 255.255.255.255.ipp: UDP,
length 160
16:05:21.569557 IP someprintserver.redhat.com.ipp > 255.255.255.255.ipp: UDP,
length 157
16:05:22.568824 IP someprintserver.redhat.com.ipp > 255.255.255.255.ipp: UDP,
length 143

At the same time in /var/log/cups/error_log:
D [19/Jul/2006:16:05:19 +0200] cupsdNetIFUpdate: "lo" = localhost...
D [19/Jul/2006:16:05:19 +0200] cupsdNetIFUpdate: "eth0" = printclient.redhat.com...
D [19/Jul/2006:16:05:19 +0200] cupsdUpdateCUPSBrowse: Refused 160 bytes from
172.16.x.x
D [19/Jul/2006:16:05:21 +0200] cupsdUpdateCUPSBrowse: Refused 157 bytes from
172.16.x.x
D [19/Jul/2006:16:05:22 +0200] cupsdUpdateCUPSBrowse: Refused 143 bytes from
172.16.x.x

Version-Release number of selected component (if applicable):
cups-1.2.1-18

How reproducible:
always