We got a similar problem. When you start libreoffice, printing work, after a short time, around 5 min, you can't print from libreoffice any more.
System kubuntu 12.04 x86 with kde 4.9.
We're printing over remote cups (cups.client), but we a local cups server the same problem appears too.
here is my /etc/cups/cupsd.conf file. Hope it'll help. (Sorry for my poor english).
LogLevel warn
MaxLogSize 1m
SystemGroup lpadmin
Listen localhost:631
Listen /var/run/cups/cups.sock
Browsing On
BrowseOrder allow,deny
BrowseAllow all
BrowseRemoteProtocols cups
BrowseLocalProtocols
DefaultAuthType Basic
WebInterface Yes
Order allow,deny
Order allow,deny
AuthType Default
Require user @SYSTEM
Order allow,deny
JobPrivateAccess default
JobPrivateValues default
SubscriptionPrivateAccess default
SubscriptionPrivateValues default
Order deny,allow
Require user @OWNER @SYSTEM
Order deny,allow
Require user @OWNER @SYSTEM
Order deny,allow
AuthType Default
Require user @SYSTEM
Order deny,allow
AuthType Default
Require user @SYSTEM
Order deny,allow
Require user @OWNER @SYSTEM
Order deny,allow
Order deny,allow
JobPrivateAccess default
JobPrivateValues default
SubscriptionPrivateAccess default
SubscriptionPrivateValues default
AuthType Default
Order deny,allow
AuthType Default
Require user @OWNER @SYSTEM
Order deny,allow
AuthType Default
Require user @SYSTEM
Order deny,allow
AuthType Default
Require user @SYSTEM
Order deny,allow
AuthType Default
Require user @OWNER @SYSTEM
Order deny,allow
Order deny,allow