Comment 1 for bug 938669

Here, an additional test Test. A new / clean Ubuntu Lucid installation:

root@ts3:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 10.04.4 LTS
Release: 10.04
Codename: lucid

I set this limits in /etc/security/limits.conf
root hard nofile 65536
root soft nofile 65536

root@ts3:~# ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 20
file size (blocks, -f) unlimited
pending signals (-i) 16382
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 65536
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) unlimited
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited

root@ts3:~# dpkg -l "cups*"
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Description
+++-==============-==============-============================================
ii cups 1.4.3-1ubuntu1 Common UNIX Printing System(tm) - server
un cups-bsd <none> (no description available)
ii cups-client 1.4.3-1ubuntu1 Common UNIX Printing System(tm) - client pro
ii cups-common 1.4.3-1ubuntu1 Common UNIX Printing System(tm) - common fil
ii cups-driver-gu 5.2.5-0ubuntu1 printer drivers for CUPS
un cups-pdf <none> (no description available)
un cups-ppdc <none> (no description available)
un cups-pt <none> (no description available)
un cupsddk <none> (no description available)
un cupsddk-driver <none> (no description available)
un cupsomatic-ppd <none> (no description available)
un cupsys <none> (no description available)
un cupsys-bsd <none> (no description available)
un cupsys-client <none> (no description available)
un cupsys-common <none> (no description available)
un cupsys-driver- <none> (no description available)

CPUS changes in /etc/cups/cupsd.conf:
LogLevel debug
MaxClients 32768

CUPS 1.4.3-1ubuntu1 works fine, like expected:

root@ts3:~# grep Max /var/log/cups/error_log
I [22/Feb/2012:18:17:23 +0100] MaxClients limited to 1/3 (21845) of the file descriptor limit (65536)...

then i change the /etc/apt/sources.list from lucid to maverick and reinstall CUPS
apt-get install cups
...
The following packages will be upgraded:
cups cups-client cups-common libcups2

root@ts3:~# dpkg -l "cups*"
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Cfg-files/Unpacked/Failed-cfg/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Description
+++-==============-==============-============================================
ii cups 1.4.4-6ubuntu2 Common UNIX Printing System(tm) - server
un cups-bsd <none> (no description available)
ii cups-client 1.4.4-6ubuntu2 Common UNIX Printing System(tm) - client pro
ii cups-common 1.4.4-6ubuntu2 Common UNIX Printing System(tm) - common fil
ii cups-driver-gu 5.2.5-0ubuntu1 printer drivers for CUPS
un cups-pdf <none> (no description available)
ii cups-ppdc 1.4.4-6ubuntu2 Common UNIX Printing System(tm) - PPD manipu
un cups-pt <none> (no description available)
un cupsddk <none> (no description available)
un cupsddk-driver <none> (no description available)
un cupsomatic-ppd <none> (no description available)
un cupsys <none> (no description available)
un cupsys-client <none> (no description available)
un cupsys-driver- <none> (no description available)

and here the error:
I [22/Feb/2012:18:21:54 +0100] MaxClients limited to 1/3 (341) of the file descriptor limit (1024)...

The only change is CUPS upgrade from 1.4.3-1ubuntu1 to 1.4.4-6ubuntu2, configuration has not changed.

BR Pawel