If I have the libvirt-slave plugin installed and try to edit one of my nodes (dummy) it throws an exception when I hit save.

Stack trace:
java.lang.RuntimeException: Failed to instantiate class hudson.slaves.DumbSlave from {"":["hudson.slaves.CommandLauncher","hudson.slaves.RetentionStrategy$Always"],"labelString":"64bot","launcher":

{"command":"/var/lib/jenkins/bin/go_slave_nunit.sh 151.155.248.175","host":"","javaPath":"","jvmOptions":"","password":["",""],"port":"22","privatekey":"","stapler-class":["hudson.os.windows.ManagedWindowsServiceLauncher","hudson.slaves.CommandLauncher","hudson.slaves.JNLPLauncher","hudson.plugins.libvirt.VirtualMachineLauncher","hudson.plugins.sshslaves.SSHLauncher"],"tunnel":"","userName":"","username":"","vmargs":""}

,"mode":"NORMAL","name":"jenkins2","nodeDescription":"build1 - 64bit machine","nodeProperties":

{"stapler-class-bag":"true"}

,"numExecutors":"5","remoteFS":"/var/lib/jenkins","retentionStrategy":{"stapler-class":"hudson.slaves.RetentionStrategy$Always"}}
at hudson.model.Descriptor.newInstance(Descriptor.java:543)
at hudson.model.Node.reconfigure(Node.java:392)
at hudson.model.Computer.doConfigSubmit(Computer.java:1035)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:282)
at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:149)
at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:88)
at org.kohsuke.stapler.MetaClass$1.doDispatch(MetaClass.java:103)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:561)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
at org.kohsuke.stapler.MetaClass$12.dispatch(MetaClass.java:373)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:561)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
at org.kohsuke.stapler.MetaClass$4.doDispatch(MetaClass.java:195)
at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:53)
at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:561)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:646)
at org.kohsuke.stapler.Stapler.invoke(Stapler.java:477)
at org.kohsuke.stapler.Stapler.service(Stapler.java:159)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:45)
at winstone.ServletConfiguration.execute(ServletConfiguration.java:249)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:335)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:378)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:94)
at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:157)
at net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:131)
at net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:82)
at org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:84)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:97)
at hudson.plugins.greenballs.GreenBallFilter.doFilter(GreenBallFilter.java:52)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:97)
at hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:65)
at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:97)
at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:86)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:47)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:84)
at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:76)
at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:164)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:81)
at winstone.FilterConfiguration.execute(FilterConfiguration.java:195)
at winstone.RequestDispatcher.doFilter(RequestDispatcher.java:368)
at winstone.RequestDispatcher.forward(RequestDispatcher.java:333)
at winstone.RequestHandlerThread.processRequest(RequestHandlerThread.java:244)
at winstone.RequestHandlerThread.run(RequestHandlerThread.java:150)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.lang.IllegalArgumentException: Failed to instantiate class hudson.slaves.DumbSlave from {"":["hudson.slaves.CommandLauncher","hudson.slaves.RetentionStrategy$Always"],"labelString":"64bot","launcher":

{"command":"/var/lib/jenkins/bin/go_slave_nunit.sh 151.155.248.175","host":"","javaPath":"","jvmOptions":"","password":["",""],"port":"22","privatekey":"","stapler-class":["hudson.os.windows.ManagedWindowsServiceLauncher","hudson.slaves.CommandLauncher","hudson.slaves.JNLPLauncher","hudson.plugins.libvirt.VirtualMachineLauncher","hudson.plugins.sshslaves.SSHLauncher"],"tunnel":"","userName":"","username":"","vmargs":""}

,"mode":"NORMAL","name":"jenkins2","nodeDescription":"build1 - 64bit machine","nodeProperties":

{"stapler-class-bag":"true"}

,"numExecutors":"5","remoteFS":"/var/lib/jenkins","retentionStrategy":{"stapler-class":"hudson.slaves.RetentionStrategy$Always"}}
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:628)
at org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:372)
at org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:368)
at hudson.model.Descriptor.newInstance(Descriptor.java:534)
... 54 more
Caused by: java.lang.IllegalArgumentException: Failed to convert the launcher parameter of the constructor public hudson.slaves.DumbSlave(java.lang.String,java.lang.String,java.lang.String,java.lang.String,hudson.model.Node$Mode,java.lang.String,hudson.slaves.ComputerLauncher,hudson.slaves.RetentionStrategy,java.util.List) throws java.io.IOException,hudson.model.Descriptor$FormException
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:622)
... 57 more
Caused by: java.lang.IllegalArgumentException: Failed to instantiate class hudson.slaves.ComputerLauncher from

{"command":"/var/lib/jenkins/bin/go_slave_nunit.sh 151.155.248.175","host":"","javaPath":"","jvmOptions":"","password":["",""],"port":"22","privatekey":"","stapler-class":["hudson.os.windows.ManagedWindowsServiceLauncher","hudson.slaves.CommandLauncher","hudson.slaves.JNLPLauncher","hudson.plugins.libvirt.VirtualMachineLauncher","hudson.plugins.sshslaves.SSHLauncher"],"tunnel":"","userName":"","username":"","vmargs":""}

at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:628)
at org.kohsuke.stapler.RequestImpl.bindJSON(RequestImpl.java:372)
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:620)
... 57 more
Caused by: java.lang.IllegalArgumentException: Class ["hudson.os.windows.ManagedWindowsServiceLauncher","hudson.slaves.CommandLauncher","hudson.slaves.JNLPLauncher","hudson.plugins.libvirt.VirtualMachineLauncher","hudson.plugins.sshslaves.SSHLauncher"] is specified in JSON, but no such class found in classLoader hudson.PluginManager$UberClassLoader
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:601)
... 59 more
Caused by: java.lang.ClassNotFoundException: ["hudson.os.windows.ManagedWindowsServiceLauncher","hudson.slaves.CommandLauncher","hudson.slaves.JNLPLauncher","hudson.plugins.libvirt.VirtualMachineLauncher","hudson.plugins.sshslaves.SSHLauncher"]
at hudson.PluginManager$UberClassLoader.findClass(PluginManager.java:642)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
at org.kohsuke.stapler.RequestImpl$TypePair.convertJSON(RequestImpl.java:596)
... 59 more