系统上线，急急急！ Hibernate 非常奇怪的问题 org.hibernate.TransactionException: JDBC rollback failed

现象：
系统刚刚部署好的当天，访问几个系统没有问题，到了第二天访问该系统便会报错：org.hibernate.TransactionException: JDBC rollback failed，这个时候再重启tomcat一切又都好用了。也可以通过下面的方法测试，重新启动tomcat，一切好用，更改服务器的日期为第二天，结果几个系统就开始报错了。

网上的解决方法如下：
方法一：上网查了一下，有人说是数据库事务的原因，要把hibernate的autocommit设为false，我找了一下这个好像要在代码里面设置，而不能通过简单的设置Hibernate的配置文件来设置，就没有继续走这条路。后来想到可能是数据库连接池的原因。
方法二：在hibernate配置文件中加入对c3p0连接池的配置，同时将c3p0-0.8.4.5.jar拷贝到应用的lib文件夹下。这里说明一下，如果没有这个配置，hibernate默认使用其自身的数据库连接池。配置后则采用第三方的c3p0连接池。
使用c3p0连接池后确实没有问题了，但是我还是不明白为什么使用默认的连接池会有问题，如果哪位大哥清楚麻烦回复一下啊，谢谢！

代码如下：
public boolean login(String userName, String password) throws Exception {
Session session = HibernateUtil.currentSession();
Transaction tx = null;
ArrayList userslist = null;
//String isActiva=null;

try {
tx = session.beginTransaction();
Query query = session.createQuery(
"from SysUser as user where user.userName=:userName and user.userPassword=:userPassword and user.isActivation=1");
query.setString("userName", userName);
query.setString("userPassword", password);
userslist = (ArrayList) query.list();

tx.commit();
} catch (Exception e) {
if (tx != null) {
//tx.rollback();
}
throw e;
} finally {
tx = null;
HibernateUtil.closeSession();
}
if (userslist == null ¦ ¦ userslist.size() == 0) {
return false;

} else {
return true;
}
}

请问高手，有没有更好的方法，以上解决的方法有效吗？现在系统上线，急急急！

tomcat,报错的异常如下：
2008-01-07 09:17:25 StandardWrapperValve[action]: Servlet.service() for servlet action threw exception
org.hibernate.TransactionException: JDBC rollback failed
at org.hibernate.transaction.JDBCTransaction.rollback(JDBCTransaction.java:170)
at com.jandar.info.dao.SysUserDAO.login(SysUserDAO.java:250)
at com.jandar.info.actions.LoginAction.execute(LoginAction.java:49)
at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:419)
at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:224)
at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1194)
at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:432)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
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 com.jandar.info.util.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:106)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:595)
Caused by: com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: Connection.close() has already been called. Invalid operation in this state.
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:888)
at com.mysql.jdbc.Connection.getMutex(Connection.java:3588)
at com.mysql.jdbc.Connection.rollback(Connection.java:5035)
at org.hibernate.transaction.JDBCTransaction.rollbackAndResetAutoCommit(JDBCTransaction.java:183)
at org.hibernate.transaction.JDBCTransaction.rollback(JDBCTransaction.java:162)
... 35 more