CentOS - Jun 2014 - CUPS Disaster: printer queues going AOL or becoming disfunctional

Software versions:
   1) Host Server: CentOS 6.5 (up to date), cups-1.4.2-50.el6_4.5.x86_64
   2) VM server:   Ubuntu 14.04 (up to date), cups 1.7.2-0ubuntu1  amd64
   3) Diskless workstations: Ubuntu 14.04 (up to date), cups 1.7.2-0ubuntu1
amd64

We have two networked (hard Ethernet, with static IP addresses) Laser 
printers, a HP LaserJet 4200 (old but works great) and a Brother Color 
MFC-9970CDW.

What happened:

I updated the Host Server (standard yum update) and then rebooted it (the
update brought in a new kernel). And then printer queues became
'disfunctional'. Printing a test page resulted in a
client-error-document-format-not-supported type of error. Deleting and
re-installing the print queues fixed it. Why did this happen? And why does
re-installing the print queues fix it? Followup question: is there a way to do
fix this from the command line? It is a royal pain to have to do this with the
web GUI, esp. since it precludes doing it remotely. 

Also, just as a side adventure, the Ubuntu VM system decided to (on its own!) 
remove the color printer. I have not clue as to  why that happened.  I did 
*uninstall* the pesky cups-browserd package (which is a total disaster for a 
server or even fixed desktop machines with fixed hardwired printers).


(Longing for the good old days of LPD! -- CUPS can be a total pain in the butt 
at times.)

-- 
Robert Heller             -- 978-544-6933 / heller@deepsoft.com
Deepwoods Software        -- http://www.deepsoft.com/
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