I have the same error that violation plugin when i run javancss on a slave :

java.io.IOException: Remote call failed
at hudson.remoting.Channel.call(Channel.java:490)
at hudson.FilePath.act(FilePath.java:625)
at hudson.plugins.helpers.BuildProxy.doPerform(BuildProxy.java:71)
at
hudson.plugins.helpers.AbstractPublisherImpl.perform(AbstractPublisherImpl.java:30)
at
hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:372)
at
hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:360)
at hudson.model.Build$RunnerImpl.post2(Build.java:183)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:345)
at hudson.model.Run.run(Run.java:943)
at hudson.model.Build.run(Build.java:112)
at hudson.model.ResourceController.execute(ResourceController.java:93)
at hudson.model.Executor.run(Executor.java:119)
Caused by: java.lang.NoClassDefFoundError:
hudson/maven/MavenBuildProxy$BuildCallable
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.lang.ClassLoader.defineClass(ClassLoader.java:465)
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:100)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:242)
at hudson.remoting.ObjectInputStreamEx.resolveClass(ObjectInputStreamEx.java:50)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1544)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1466)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1699)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1305)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:348)
at hudson.remoting.UserRequest.perform(UserRequest.java:84)
at hudson.remoting.UserRequest.perform(UserRequest.java:46)
at hudson.remoting.Request$2.run(Request.java:236)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:417)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:269)
at java.util.concurrent.FutureTask.run(FutureTask.java:123)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
at hudson.remoting.Engine$1$1.run(Engine.java:54)
at java.lang.Thread.run(Thread.java:595)
FATAL: Unexpected exception
java.lang.RuntimeException: Unexpected exception
at hudson.plugins.helpers.BuildProxy.unwrapException(BuildProxy.java:118)
at hudson.plugins.helpers.BuildProxy.doPerform(BuildProxy.java:80)
at
hudson.plugins.helpers.AbstractPublisherImpl.perform(AbstractPublisherImpl.java:30)
at
hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:372)
at
hudson.model.AbstractBuild$AbstractRunner.performAllBuildStep(AbstractBuild.java:360)
at hudson.model.Build$RunnerImpl.post2(Build.java:183)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:345)
at hudson.model.Run.run(Run.java:943)
at hudson.model.Build.run(Build.java:112)
at hudson.model.ResourceController.execute(ResourceController.java:93)
at hudson.model.Executor.run(Executor.java:119)
Caused by: java.io.IOException: Remote call failed
at hudson.remoting.Channel.call(Channel.java:490)
at hudson.FilePath.act(FilePath.java:625)
at hudson.plugins.helpers.BuildProxy.doPerform(BuildProxy.java:71)
... 9 more
Caused by: java.lang.NoClassDefFoundError:
hudson/maven/MavenBuildProxy$BuildCallable
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.lang.ClassLoader.defineClass(ClassLoader.java:465)
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:100)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:242)
at hudson.remoting.ObjectInputStreamEx.resolveClass(ObjectInputStreamEx.java:50)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1544)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1466)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1699)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1305)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:348)
at hudson.remoting.UserRequest.perform(UserRequest.java:84)
at hudson.remoting.UserRequest.perform(UserRequest.java:46)
at hudson.remoting.Request$2.run(Request.java:236)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:417)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:269)
at java.util.concurrent.FutureTask.run(FutureTask.java:123)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
at hudson.remoting.Engine$1$1.run(Engine.java:54)
at java.lang.Thread.run(Thread.java:595)