SYMPTOMS:

• http://localhost:8080 doesn't accept a connection following new install via OSX platform-specific package.
• sudo launchctl unload -w /Library/LaunchDaemons/org.jenkins-ci.plist returns
  "org.jenkins-ci: Already loaded"

SUSPECTED CAUSE:
Java runtime not installed.
/usr/bin/java exists and is in PATH, but running `java` from the command line returns
"No Java runtime present, requesting install."
Running java directly from the command line produces a pop-up alert prompting to install Java. However, the failing LaunchDaemon dies silently.

LOG snippet from /var/logs/jenkins/jenkins.log:
2013-11-13 23:24:14.940 defaults[9590:507]
The domain/default pair of (/Library/Preferences/org.jenkins-ci, war) does not exist
2013-11-13 23:24:14.974 defaults[9597:507]
The domain/default pair of (/Library/Preferences/org.jenkins-ci, JENKINS_HOME) does not exist
2013-11-13 23:24:14.982 defaults[9598:507]
The domain/default pair of (/Library/Preferences/org.jenkins-ci, prefix) does not exist
2013-11-13 23:24:15.003 defaults[9601:507]
The domain/default pair of (/Library/Preferences/org.jenkins-ci, httpsPort) does not exist
2013-11-13 23:24:15.011 defaults[9602:507]
The domain/default pair of (/Library/Preferences/org.jenkins-ci, httpsListenAddress) does not exist
2013-11-13 23:24:15.019 defaults[9603:507]
The domain/default pair of (/Library/Preferences/org.jenkins-ci, ajp13Port) does not exist
2013-11-13 23:24:15.027 defaults[9604:507]
The domain/default pair of (/Library/Preferences/org.jenkins-ci, ajp13ListenAddress) does not exist
JENKINS_HOME=/Users/Shared/Jenkins/Home
Jenkins command line for execution:
/usr/bin/java -XX:PermSize=256m -XX:MaxPermSize=512m -Xms256m -Xmx512m -jar /Applications/Jenkins/jenkins.war --httpPort=8080 --httpListenAddress=localhost
No Java runtime present, requesting install.
2013-11-13 23:24:15.039 java[9589:d0b] JLRequestRuntimeInstall: Error calling: CFMessagePortCreateRemote

May be similar to JENKINS-19936