The upgrade of the Commons Codec lib from 1.4 to 1.7 with Jenkins 1.500 break the compatibility to build with JDK5.

The build fails with

[INFO] ------------------------------------------------------------------------
[ERROR] FATAL ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Failed to load org.apache.commons.codec.DecoderException
Bad version number in .class file
[INFO] ------------------------------------------------------------------------
[INFO] Trace
java.lang.ClassFormatError: Failed to load org.apache.commons.codec.DecoderException
at hudson.remoting.RemoteClassLoader.loadClassFile(RemoteClassLoader.java:193)
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:144)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.Thread.run(Thread.java:595)
...
Caused by: java.lang.UnsupportedClassVersionError: Bad version number in .class file
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
at java.lang.ClassLoader.defineClass(ClassLoader.java:466)
at hudson.remoting.RemoteClassLoader.loadClassFile(RemoteClassLoader.java:191)

Replacing Commons Codec 1.7 with 1.6 seems to fix the problem.
On the Commons Codec site (http://commons.apache.org/codec/) the following compatibility notes can be found:

Codec 1.7 requires Java 1.6
Codec 1.6 requires Java 1.5
Codec 1.5 requires Java 1.4

So please downgrade to Commons Codec 1.6 if possible.