Erro servlet.init()

Alguém já teve um erro parecido com este?

HTTP Status 500 -

---

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Servlet.init() for servlet ContatoClienteServlet threw exception

org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)

org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:212)

org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:818)

org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:624)

org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)

java.lang.Thread.run(Unknown Source)

root cause

java.lang.UnsupportedClassVersionError: Bad version number in .class file

java.lang.ClassLoader.defineClass1(Native Method)

java.lang.ClassLoader.defineClass(Unknown Source)

java.security.SecureClassLoader.defineClass(Unknown Source)

org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1810)

org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:869)

org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1322)

org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1201)

java.lang.ClassLoader.loadClassInternal(Unknown Source)

br.com.bb.sig.ContatoClienteServlet.initCommands(ContatoClienteServlet.java:80)

br.com.bb.sig.ContatoClienteServlet.init(ContatoClienteServlet.java:38)

javax.servlet.GenericServlet.init(GenericServlet.java:212)

org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)

org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:212)

org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:818)

org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:624)

org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:445)

java.lang.Thread.run(Unknown Source)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.2 logs.

agradeço a ajuda