tomcat 500错误

软件环境:
webserver:tomcat5.0
jdk:      jdk1.5
数据库:   oracle9i
开发工具: myeclipse
问题如下：
在我的主页面有3个iframe,每个iframe下有个jsp文件
当我加载页面的时候，其中框架下的一个页面，报500错误,但是有时候是正常的，大多数情况下是正常的
错误如下：
type Exception report

message

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

exception

javax.servlet.ServletException: com/asiainfo/omnivison/vgop/service/KpiChartServiceImpl
    org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:825)
    org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:758)
    org.apache.jsp.kpi.kpiTrend_005fnyg_jsp._jspService(kpiTrend_005fnyg_jsp.java:150)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
    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)
    com.asiainfo.servlet.SetLogDetailFilter.doFilter(SetLogDetailFilter.java:49)


root cause

java.lang.NoClassDefFoundError: com/asiainfo/omnivison/vgop/service/KpiChartServiceImpl
    org.apache.jsp.kpi.kpiTrend_005fnyg_jsp._jspService(kpiTrend_005fnyg_jsp.java:85)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
    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)
    com.asiainfo.servlet.SetLogDetailFilter.doFilter(SetLogDetailFilter.java:49)


note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.
望大家能够伸出援手，谢谢

com/asiainfo/omnivison/vgop/service/KpiChartServiceImpl
没有找到这个类，注意路径

路径是没有什么问题的，只是在服务器刚一启动的时候，第一次用这个类的时候出现这种错误
但是以后就没有问题了

反正只要服务器一启动的时候，第一次用，就出现这种找不到的错误