Who can tell me this is any error?

Log File:

2013.10.13 02:07:31 org.jivesoftware.openfire.handler.IQHandler - Internal server error

java.lang.IllegalArgumentException: IQ must be of type ‘set’ or ‘get’. Original IQ:

at org.xmpp.packet.IQ.createResultIQ(IQ.java:384)

at org.jivesoftware.openfire.handler.IQPingHandler.handleIQ(IQPingHandler.java:58)

at org.jivesoftware.openfire.handler.IQHandler.process(IQHandler.java:65)

at org.jivesoftware.openfire.IQRouter.handle(IQRouter.java:374)

at org.jivesoftware.openfire.IQRouter.route(IQRouter.java:121)

at org.jivesoftware.openfire.spi.PacketRouterImpl.route(PacketRouterImpl.java:76)

at org.jivesoftware.openfire.net.StanzaHandler.processIQ(StanzaHandler.java:337)

at org.jivesoftware.openfire.net.ClientStanzaHandler.processIQ(ClientStanzaHandler .java:93)

at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.java:302)

at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.java:194)

at org.jivesoftware.openfire.nio.ConnectionHandler.messageReceived(ConnectionHandl er.java:181)

at org.apache.mina.common.support.AbstractIoFilterChain$TailFilter.messageReceived (AbstractIoFilterChain.java:570)

at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:299)

at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:53)

at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:648)

at org.apache.mina.common.IoFilterAdapter.messageReceived(IoFilterAdapter.java:80)

at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:299)

at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:53)

at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:648)

at org.apache.mina.filter.codec.support.SimpleProtocolDecoderOutput.flush(SimplePr otocolDecoderOutput.java:58)

at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecF ilter.java:185)

at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:299)

at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:53)

at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:648)

at org.apache.mina.filter.executor.ExecutorFilter.processEvent(ExecutorFilter.java :239)

at org.apache.mina.filter.executor.ExecutorFilter$ProcessEventsRunnable.run(Execut orFilter.java:283)

at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

at org.apache.mina.util.NamePreservingRunnable.run(NamePreservingRunnable.java:51)

at java.lang.Thread.run(Unknown Source)