java.lang.VerifyErrorが解決できません。

eclipse3.7,java1.6でwebアプリケーションを修正しています。Tomcat7.0.81を起動すると次のようなエラーが表示されてしまいます。(Tomcat6.0.36では問題なく起動し表示されていました。)
Tomcatプロジェクトにコンテキストを追加すると以下のような状態になります。
どのように解決すればいいでしょうか？

###発生している問題・エラーメッセージ

致命的: Begin event threw error
java.lang.VerifyError: class org.apache.catalina.loader.DevLoader overrides final method start.()V
	at java.lang.ClassLoader.defineClass1(Native Method)
	at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
	at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
	at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
	at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
	at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
	at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
	at org.apache.tomcat.util.digester.ObjectCreateRule.begin(ObjectCreateRule.java:144)
	at org.apache.tomcat.util.digester.Digester.startElement(Digester.java:1303)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:501)
	at com.sun.org.apache.xerces.internal.parsers.AbstractXMLDocumentParser.emptyElement(AbstractXMLDocumentParser.java:179)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:1343)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(XMLDocumentFragmentScannerImpl.java:2755)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(XMLDocumentScannerImpl.java:648)
	at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:511)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:808)
	at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:737)
	at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:119)
	at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1205)
	at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(SAXParserImpl.java:522)
	at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1576)
	at org.apache.catalina.startup.ContextConfig.processContextConfig(ContextConfig.java:651)
	at org.apache.catalina.startup.ContextConfig.contextConfig(ContextConfig.java:613)
	at org.apache.catalina.startup.ContextConfig.init(ContextConfig.java:849)
	at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:399)
	at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
	at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
	at org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:388)
	at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:103)
	at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:135)
	at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:1009)
	at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:985)
	at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
	at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:712)
	at org.apache.catalina.startup.HostConfig$DeployDescriptor.run(HostConfig.java:2002)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
	at java.util.concurrent.FutureTask.run(FutureTask.java:138)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:662)