ComputerLauncher.checkJavaVersion should be ensuring that the slave is Java 6+, since Java 5 is no longer supported for a slave agent.

core/src/main/java/hudson/slaves/ComputerLauncher.java

@@ -183,7 +183,7 @@ public abstract class ComputerLauncher extends AbstractDescribableImpl<ComputerL
                 final String versionStr = m.group(1);
                 logger.println(Messages.ComputerLauncher_JavaVersionResult(javaCommand, versionStr));
                 try {
-                    if (new DeweyDecimal(versionStr).isLessThan(new DeweyDecimal("1.5"))) {
+                    if (new DeweyDecimal(versionStr).isLessThan(new DeweyDecimal("1.6"))) {
                         throw new IOException(Messages
                                 .ComputerLauncher_NoJavaFound(line));
                     }

core/src/main/resources/hudson/slaves/Messages.properties

@@ -39,6 +39,6 @@ SimpleScheduledRetentionStrategy.displayName=Take this slave on-line according t
 EnvironmentVariablesNodeProperty.displayName=Environment variables
 SlaveComputer.DisconnectedBy=Disconnected by {0}{1}
 NodeDescripter.CheckName.Mandatory=Name is mandatory
-ComputerLauncher.NoJavaFound=Java version {0} was found but 1.5 or later is needed.
+ComputerLauncher.NoJavaFound=Java version {0} was found but 1.6 or later is needed.
 ComputerLauncher.JavaVersionResult={0} -version returned {1}.
 ComputerLauncher.UknownJavaVersion=Couldn\u2019t figure out the Java version of {0}