项目发布到服务器上的问题，本地测试功过。

本机运行 jdk1.5 + tomcat5.5
开始开始的时候，部署到服务器上是正确，但是过了几天突然就出现这个问题了。
现在服务处于停滞状态，还请处理一下，我已经处理了一天一夜了，没有结果。
希望大家能帮忙处理以下。
log4 日志如下：
[INFO ] 2007-01-25 09:55:22,062 method:org.hibernate.cfg.Environment.<clinit>(Environment.java:479)
Hibernate 3.1.3
[INFO ] 2007-01-25 09:55:22,093 method:org.hibernate.cfg.Environment.<clinit>(Environment.java:509)
hibernate.properties not found
[INFO ] 2007-01-25 09:55:22,109 method:org.hibernate.cfg.Environment.<clinit>(Environment.java:525)
using CGLIB reflection optimizer
[INFO ] 2007-01-25 09:55:22,109 method:org.hibernate.cfg.Environment.<clinit>(Environment.java:555)
using JDK 1.4 java.sql.Timestamp handling
[INFO ] 2007-01-25 09:55:22,359 method:org.hibernate.cfg.Configuration.configure(Configuration.java:1308)
configuring from resource: /hibernate.cfg.xml
[INFO ] 2007-01-25 09:55:22,359 method:org.hibernate.cfg.Configuration.getConfigurationInputStream(Configuration.java:1285)
Configuration resource: /hibernate.cfg.xml
[WARN ] 2007-01-25 09:55:22,515 method:org.hibernate.util.XMLHelper$ErrorLogger.warning(XMLHelper.java:68)
Warning parsing XML: /hibernate.cfg.xml(1) Valid documents must have a <!DOCTYPE declaration.
[ERROR] 2007-01-25 09:55:22,515 method:org.hibernate.util.XMLHelper$ErrorLogger.error(XMLHelper.java:61)
Error parsing XML: /hibernate.cfg.xml(1) Document root element is missing.
[ERROR] 2007-01-25 09:55:22,531 method:org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:260)
Servlet.service() for servlet BlogIndex threw exception
java.lang.NullPointerException
at connection.HibConnection.currentSession(HibConnection.java:56)
at bean.ProductBean.getProductListByMainType(ProductBean.java:1207)
at blog.bean.IndexBean.<init>(IndexBean.java:48)
at blog.servlet.BlogIndexServlet.doGet(BlogIndexServlet.java:34)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)