I tried this multiple times: slaves fail to connect when using version 1.519 or later; the same slaves connects fine when using 1.518 or earlier (as early as 1.501).

The experiments were done with a simple jenkins with no jobs configured, and with only the master and a couple of slaves.

Log shows the following error:

...
[07/16/13 15:39:19] [SSH] Checking java version of java
[07/16/13 15:39:19] [SSH] java -version returned 1.6.0_10.
[07/16/13 15:39:19] [SSH] Starting sftp client.
[07/16/13 15:39:19] [SSH] Copying latest slave.jar...
[07/16/13 15:39:19] [SSH] Copied 326,006 bytes.
Expanded the channel window size to 4MB
[07/16/13 15:39:19] [SSH] Starting slave process: cd '/data00/hudson_home_analysis' && java -jar slave.jar
<===[JENKINS REMOTING CAPACITY]===>channel started
Slave.jar version: 2.24
This is a Unix slave
hudson.util.IOException2: Failed to copy /jenkins/data/plugins/maven-plugin/WEB-INF/lib/maven-agent-1.3.jar to /hudson_home/maven-agent.jar
at hudson.FilePath.copyTo(FilePath.java:1726)
at hudson.maven.MavenComputerListener.copyJar(MavenComputerListener.java:90)
at hudson.maven.MavenComputerListener.preOnline(MavenComputerListener.java:57)
at hudson.slaves.SlaveComputer.setChannel(SlaveComputer.java:469)
at hudson.slaves.SlaveComputer.setChannel(SlaveComputer.java:343)
at hudson.plugins.sshslaves.SSHLauncher.startSlave(SSHLauncher.java:712)
at hudson.plugins.sshslaves.SSHLauncher.launch(SSHLauncher.java:498)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:226)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
Caused by: java.io.IOException: Remote call on repo-01 failed
at hudson.remoting.Channel.call(Channel.java:731)
at hudson.FilePath.write(FilePath.java:1625)
at hudson.FilePath.copyTo(FilePath.java:1719)
... 12 more
Caused by: java.lang.NoClassDefFoundError: org/apache/commons/io/input/ProxyInputStream
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:289)
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:229)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
at java.lang.Class.getDeclaredFields0(Native Method)
at java.lang.Class.privateGetDeclaredFields(Class.java:2291)
at java.lang.Class.getDeclaredField(Class.java:1880)
at java.io.ObjectStreamClass.getDeclaredSUID(ObjectStreamClass.java:1610)
at java.io.ObjectStreamClass.access$700(ObjectStreamClass.java:52)
at java.io.ObjectStreamClass$2.run(ObjectStreamClass.java:425)
at java.security.AccessController.doPrivileged(Native Method)
at java.io.ObjectStreamClass.<init>(ObjectStreamClass.java:413)
at java.io.ObjectStreamClass.lookup(ObjectStreamClass.java:310)
at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:547)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1583)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1496)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1732)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1947)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1871)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1753)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1329)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at hudson.remoting.UserRequest.deserialize(UserRequest.java:182)
at hudson.remoting.UserRequest.perform(UserRequest.java:98)
at hudson.remoting.UserRequest.perform(UserRequest.java:48)
at hudson.remoting.Request$2.run(Request.java:326)
at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72)
... 5 more
Caused by: java.lang.ClassNotFoundException: org.apache.commons.io.input.ProxyInputStream
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:237)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 37 more
Caused by: java.util.concurrent.ExecutionException: java.util.zip.ZipException: error in opening zip file
at hudson.remoting.ResourceImageInJar$1.adapt(ResourceImageInJar.java:48)
at hudson.remoting.ResourceImageInJar$1.adapt(ResourceImageInJar.java:42)
at hudson.remoting.FutureAdapter.get(FutureAdapter.java:55)
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:229)
... 40 more
Caused by: java.util.zip.ZipException: error in opening zip file
at java.util.zip.ZipFile.open(Native Method)
at java.util.zip.ZipFile.<init>(ZipFile.java:114)
at java.util.jar.JarFile.<init>(JarFile.java:133)
at java.util.jar.JarFile.<init>(JarFile.java:70)
at sun.net.www.protocol.jar.URLJarFile.<init>(URLJarFile.java:72)
at sun.net.www.protocol.jar.URLJarFile.getJarFile(URLJarFile.java:48)
at sun.net.www.protocol.jar.JarFileFactory.get(JarFileFactory.java:53)
at sun.net.www.protocol.jar.JarURLConnection.connect(JarURLConnection.java:104)
at sun.net.www.protocol.jar.JarURLConnection.getInputStream(JarURLConnection.java:132)
at java.net.URL.openStream(URL.java:1009)
at hudson.remoting.ResourceImageInJar$1.adapt(ResourceImageInJar.java:46)
... 43 more
[07/16/13 15:39:20] [SSH] Connection closed.
ERROR: Connection terminated
java.io.IOException: Unexpected termination of the channel
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:50)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2554)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at hudson.remoting.Command.readFrom(Command.java:92)
at hudson.remoting.ClassicCommandTransport.read(ClassicCommandTransport.java:59)
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:48)
ERROR: [07/16/13 15:39:20] slave agent was terminated
java.io.IOException: Unexpected termination of the channel
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:50)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2554)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1297)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:351)
at hudson.remoting.Command.readFrom(Command.java:92)
at hudson.remoting.ClassicCommandTransport.read(ClassicCommandTransport.java:59)
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:48)