I tried it with various jetty versions and Netbeans 7.0.1 --it doesn't work.

2011-12-28 14:57:02.774:WARN:oejj.MBeanContainer:bean: org.eclipse.jetty.jmx.MBeanContainer@1124746#STARTED
javax.management.InstanceAlreadyExistsException: org.eclipse.jetty.jmx:type=mbeancontainer,id=0
at com.sun.jmx.mbeanserver.Repository.addMBean(Repository.java:453)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.internal_addObject(DefaultMBeanServerInterceptor.java:1484)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerDynamicMBean(DefaultMBeanServerInterceptor.java:963)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerObject(DefaultMBeanServerInterceptor.java:917)
at com.sun.jmx.interceptor.DefaultMBeanServerInterceptor.registerMBean(DefaultMBeanServerInterceptor.java:312)
at com.sun.jmx.mbeanserver.JmxMBeanServer.registerMBean(JmxMBeanServer.java:482)
at org.eclipse.jetty.jmx.MBeanContainer.addBean(MBeanContainer.java:300)
at org.eclipse.jetty.util.component.Container.addBean(Container.java:177)
at org.eclipse.jetty.server.Server.addBean(Server.java:50

I can confirm that problem!
I've tried with both 7 and 8 version.
Netbeans 7.0.1

IT DOES NOT WORK; I HAVE A BIND EXCEPTION (AND NO, I HAVE NOT THE PORT IN USE).
IF I START IT MANUALLY, ALL WORKS FINE.
I've changed the http & rmi ports too, but nothing.

I'm under linux.

The jetty version is 7.4.0

The extract of netbeans output window.

2011-04-22 16:56:49.903:INFO::jetty-7.4.0.v20110414
2011-04-22 16:56:49.923:INFO::Deployment monitor /home/XX/netbeans/jetty-distribution-7.4.0.v20110414/webapps at interval 1
2011-04-22 16:56:49.927:INFO::Deployment monitor /home/XX/netbeans/jetty-distribution-7.4.0.v20110414/contexts at interval 1
2011-04-22 16:56:49.929:INFO::Deployable added: /home/XX/netbeans/jetty-distribution-7.4.0.v20110414/contexts/test.xml
2011-04-22 16:56:50.057:INFO::Extract jar:file:/home/XX/netbeans/jetty-distribution-7.4.0.v20110414/webapps/test.war!/ to /tmp/jetty-0.0.0.0-8087-test.war-_-any-/webapp

2011-04-22 16:56:50.778:INFO::started o.e.j.w.WebAppContext{/,file:/tmp/jetty-0.0.0.0-8087-test.war-_-any-/webapp/},/home/XX/netbeans/jetty-distribution-7.4.0.v20110414/webapps/test.war

2011-04-22 16:56:51.529:INFO:org.eclipse.jetty.servlets.TransparentProxy:TransparentProxy @ /javadoc to http://download.eclipse.org/jetty/stable-7/apidocs
2011-04-22 16:56:51.531:INFO::Deployable added: /home/XX/netbeans/jetty-distribution-7.4.0.v20110414/contexts/javadoc.xml
2011-04-22 16:56:51.555:INFO::started o.e.j.s.h.ContextHandler{/javadoc,file:/home/XX/netbeans/jetty-distribution-7.4.0.v20110414/javadoc}
2011-04-22 16:56:51.589:INFO::Started SelectChannelConnector@0.0.0.0:8087 STARTING
2011-04-22 16:56:51.591:WARN::FAILED SelectChannelConnector@0.0.0.0:8087 FAILED: java.net.BindException: Address already in use
2011-04-22 16:56:51.593:WARN::FAILED org.eclipse.jetty.server.Server@a09e41: java.net.BindException: Address already in use
java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccesso
rImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.eclipse.jetty.start.Main.invokeMain(Main.java:477)
at org.eclipse.jetty.start.Main.start(Main.java:623)
at org.eclipse.jetty.start.Main.parseCommandLine(Main.java:273)
at org.eclipse.jetty.start.Main.main(Main.java:81)
Caused by: java.net.BindException: Address already in use
at sun.nio.ch.Net.bind(Native Method)
at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:126)
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:59)
at org.eclipse.jetty.server.nio.SelectChannelConnector.open(SelectChannelConnector.java:172)
at org.eclipse.jetty.server.AbstractConnector.doStart(AbstractConnector.java:304)
at org.eclipse.jetty.server.nio.SelectChannelConnector.doStart(SelectChannelConnector.java:250)
at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:58)
at org.eclipse.jetty.server.Server.doStart(Server.java:264)
at org.eclipse.jetty.util.component.AbstractLifeCycle.star
t(AbstractLifeCycle.java:58)
at org.eclipse.jetty.xml.XmlConfiguration$1.run(XmlConfiguration.java:1220)
at java.security.AccessController.doPrivileged(Native Method)
at org.eclipse.jetty.xml.XmlConfiguration.main(XmlConfiguration.java:1143)
... 8 more

Usage: java -jar start.jar [options] [properties] [configs]
java -jar start.jar --help # for more information
2011-04-22 16:56:51.594:INFO::Graceful shutdown SelectChannelConnector@0.0.0.0:8087 FAILED
2011-04-22 16:56:51.594:INFO::Graceful shutdown SelectChannelConnector@0.0.0.0:8087 STARTED