jenkins fails to start in Quantal: java.lang.UnsupportedClassVersionError: javax/jmdns/JmDNS : Unsupported major.minor version 51.0

Fresh installation of jenkins on Quantal, first access from a browser returns the following error:
"""
Exception in thread "hudson initialization thread" java.lang.UnsupportedClassVersionError: javax/jmdns/JmDNS : Unsupported major.minor version 51.0
 at java.lang.ClassLoader.defineClass1(Native Method)
 at java.lang.ClassLoader.defineClass(ClassLoader.java:634)
 at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
 at java.net.URLClassLoader.defineClass(URLClassLoader.java:277)
 at java.net.URLClassLoader.access$000(URLClassLoader.java:73)
 at java.net.URLClassLoader$1.run(URLClassLoader.java:212)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
 at hudson.DNSMultiCast.<init>(DNSMultiCast.java:26)
 at jenkins.model.Jenkins.<init>(Jenkins.java:757)
 at hudson.model.Hudson.<init>(Hudson.java:81)
 at hudson.model.Hudson.<init>(Hudson.java:77)
 at hudson.WebAppMain$2.run(WebAppMain.java:217)
"""

Log file attached

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: jenkins 1.447.1+dfsg-1
ProcVersionSignature: Ubuntu 3.4.0-3.8-generic 3.4.0
Uname: Linux 3.4.0-3-generic x86_64
ApportVersion: 2.1.1-0ubuntu2
Architecture: amd64
Date: Sat Jun 2 20:53:19 2012
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: jenkins
UpgradeStatus: Upgraded to quantal on 2012-01-31 (122 days ago)