I have an error with java/solr when the traffic grows up.

It seems Solr tries to cast a java.lang.Object to a org.apache.solr.common.util.ConcurrentLRUCache$CacheEntry

SEVERE: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to [Lorg.apache.solr.common.util.ConcurrentLRUCache$CacheEntry;
    at org.apache.solr.common.util.ConcurrentLRUCache$PQueue.myInsertWithOverflow(ConcurrentLRUCache.java:377)
    at org.apache.solr.common.util.ConcurrentLRUCache.markAndSweep(ConcurrentLRUCache.java:329)
    at org.apache.solr.common.util.ConcurrentLRUCache.put(ConcurrentLRUCache.java:144)
    at org.apache.solr.search.FastLRUCache.put(FastLRUCache.java:131)
    at org.apache.solr.search.SolrIndexSearcher.getDocSet(SolrIndexSearcher.java:573)
    at org.apache.solr.search.SolrIndexSearcher.getDocSet(SolrIndexSearcher.java:641)
    at org.apache.solr.search.SolrIndexSearcher.getDocListNC(SolrIndexSearcher.java:1109)
    at org.apache.solr.search.SolrIndexSearcher.getDocListC(SolrIndexSearcher.java:1090)
    at org.apache.solr.search.SolrIndexSearcher.search(SolrIndexSearcher.java:337)
    at org.apache.solr.handler.component.QueryComponent.process(QueryComponent.java:431)
    at org.apache.solr.handler.component.SearchHandler.handleRequestBody(SearchHandler.java:231)
    at org.apache.solr.handler.RequestHandlerBase.handleRequest(RequestHandlerBase.java:129)
    at org.apache.solr.core.SolrCore.execute(SolrCore.java:1298)
    at org.apache.solr.servlet.SolrDispatchFilter.execute(SolrDispatchFilter.java:340)
    at org.apache.solr.servlet.SolrDispatchFilter.doFilter(SolrDispatchFilter.java:240)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:470)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:857)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Thread.java:636)

This is my java configuration for tomcat

JAVA_OPTS="-Djava.awt.headless=true -D64 -server -Xms4096M -Xmx4096M -XX:+UseConcMarkSweepGC -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=5400 -Dcom.sun.management.jmxremote.ss\
l=false -Dcom.sun.management.jmxremote.authenticate=false"

Somebody know why these errors happen ?