for starters Fedora 12 is 5 versions ( soon SIX versions) OUT OF DATE
the current Fedora is Fedora 17 with fedora 18 do in November
fedora 12 has NOT had any security updates in years
and no new software will run on it
it is DEAD and UNSUPPORTED
the current ns-allinone is in the fedora 17 repos
BUT
If you MUST use a dead and unsupported and UNPATCHED operating system
( NOT RECOMMENDED!!!)
then see the Fedoraforum " End Of Life" thread
http://forums.fedoraforum.org/forumdisplay.php?f=75
and the VERY first thing you need to do is READ the sticky
please READ first
http://forums.fedoraforum.org/showthread.php?t=233942