请教:这个错误怎么解决啊 ( 积分: 50 )

这是在myeclipse+tomact5.0发生的错误:
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type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: XML parsing error on file /WEB-INF/web.xml: (line 4, col -1)
org.apache.jasper.xmlparser.ParserUtils.parseXMLDocument(ParserUtils.java:103)
org.apache.jasper.compiler.JspConfig.processWebDotXml(JspConfig.java:70)
org.apache.jasper.compiler.JspConfig.init(JspConfig.java:188)
org.apache.jasper.compiler.JspConfig.findJspProperty(JspConfig.java:240)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:160)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:470)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

root cause
java.lang.IllegalStateException: can't declare any more prefixes in this context
org.apache.crimson.parser.Parser2.parseInternal(Parser2.java:524)
org.apache.crimson.parser.Parser2.parse(Parser2.java:305)
org.apache.crimson.parser.XMLReaderImpl.parse(XMLReaderImpl.java:442)
org.apache.crimson.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:185)
javax.xml.parsers.DocumentBuilder.parse(Unknown Source)
org.apache.jasper.xmlparser.ParserUtils.parseXMLDocument(ParserUtils.java:98)
org.apache.jasper.compiler.JspConfig.processWebDotXml(JspConfig.java:70)
org.apache.jasper.compiler.JspConfig.init(JspConfig.java:188)
org.apache.jasper.compiler.JspConfig.findJspProperty(JspConfig.java:240)
org.apache.jasper.compiler.Compiler.generateJava(Compiler.java:160)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:470)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:451)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:439)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:511)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:295)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs
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什么原因啊??请赐教????