The server encountered an internal error () that prevented it from fulfilling this request是什么错误

执行jsp的时候报这个错
description 
The server encountered an internal error () that prevented it from fulfilling this request.exception 
org.apache.jasper.JasperException org.apache.jasper.servlet.JspServletWrapper.servic(JspServletWrapper.java:358)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)root cause 
java.lang.NullPointerException
org.apache.jsp.chatRoom.user_005freg_005fform_jsp._jspService(user_005freg_005fform_jsp.java:67)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)这是什么错误啊
我的代码如下：
<%@ page contentType="text/html; charset=gb2312" language="java"%>
<%@ page import="java.sql.*"%>
<! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html14/loose.dtd">
<%
String sUserName=null;
String sUserPassword=null;
String sSex=null;
String sNickName=null;
String strSql=null;
ResultSet rs=null;
%>
<html>
<head>
<mta http-equiv="Content-Type" content="text/html;charset=gb2312">
<title>欢迎光临聊天室</title>
<jsp:useBean scope="page" id="ExecuteDB" class="com.bean.ExecuteDB" />
</head>
<body bgcolor="#dffdff">
<div align="center">
<h1>用户注册</h1>
<%
request.setCharacterEncoding("gb2312");
sUserName=request.getParameter("UserName");

strSql="select * from users where UserName like '" +sUserName+ "' ";

rs=ExecuteDB.exeQuery(strSql);
if(!rs.next())
{
sUserPassword=request.getParameter("UserPassword");
sSex=request.getParameter("sex");
sNickName=request.getParameter("userNick");

strSql="insert into users (UserName,UserPassword,sex,NickName) values('"+sUserName+"','"+sUserPassword+"','"+sSex+"','"+sNickName+"')";
if(ExecuteDB.exeSql(strSql))
{//信息保存成功
out.println("<p><font color=blue>注册成功</font></P>");
out.println("<p><input type=\"button\"name=\"btn\"value=\"回到首页\"onClick=\"javascript:window.loction='index.html'\"></p>");
}
else
{//注册信息失败
out.println("<p><font color=blue>注册失败</font></p>");
out.println("<p><font color=red>"+ExecuteDB.getErrMes()+"</font><p>");
out.println("<p><input type=\"button\"name=\"btn\"value=\"返回\"onClick=\"javascript:window.history.go(-1)\"></p>");
}
}
else
{//用户名存在
out.println("<p>用户名 &nbsp;<font color=blue>"+sUserName+"</font>&nbsp;已存在</p>");
out.println("<p><input type=\"button\"name=\"btn\"value=\"重新输入\"onClick=\"javascript:window.history.go(-1)\"></p>");
}
rs.close();
%>
</div>
</div>
</body>
</html>