请问一下，这个异常是怎么造成的？？

我用jsp+javabean写了个小型论坛网站，但在打开 动态生成的网页 的时候，
经常会抛出下边的异常，但是一“刷新”，就又可以正常显示了。这是怎么
回事呢？？ 我阅读了异常的最后几行，似乎是说线程出现了问题，我想另外问一下：
是不是动态生成的网页都要用 synchronized(application){ }进行同步啊！！？？java.io.IOException: tmpFile.renameTo(classFile) failed
        at org.apache.jasper.compiler.SmapUtil$SDEInstaller.install(SmapUtil.jav
a:241)
        at org.apache.jasper.compiler.SmapUtil.installSmap(SmapUtil.java:163)
        at org.apache.jasper.compiler.Compiler.generateClass(Compiler.java:449)
        at org.apache.jasper.compiler.Compiler.compile(Compiler.java:492)
        at org.apache.jasper.compiler.Compiler.compile(Compiler.java:471)
        at org.apache.jasper.compiler.Compiler.compile(Compiler.java:459)
        at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext
.java:511)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper
.java:295)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:2
92)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:237)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:157)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:214)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.StandardContextValve.invokeInternal(Standard
ContextValve.java:198)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:152)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:137)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:118)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:102)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:109)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValv
eContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.jav
a:520)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)        at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:16
0)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java
:799)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.proce
ssConnection(Http11Protocol.java:705)
        at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java
:577)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadP
ool.java:684)
        at java.lang.Thread.run(Thread.java:534)