sql问题

本人开发的b/s系统，java + tomcat + sql server 2000 数据库已经打上sp4补丁，系统运行一段时间以后，常会出现 数据库无法连接 ，报的错有：
java.sql.SQLException: [Microsoft][SQLServer 2000 Driver for JDBC]Error establishing socket.
at com.microsoft.jdbc.base.BaseExceptions.createException(Unknown Source)
at com.microsoft.jdbc.base.BaseExceptions.getException(Unknown Source)
at com.microsoft.jdbc.base.BaseExceptions.getException(Unknown Source)
at com.microsoft.jdbc.sqlserver.tds.TDSConnection.<init>(Unknown Source)
at com.microsoft.jdbc.sqlserver.SQLServerImplConnection.open(Unknown Source)
at com.microsoft.jdbc.base.BaseConnection.getNewImplConnection(Unknown Source)
at com.microsoft.jdbc.base.BaseConnection.open(Unknown Source)
at com.microsoft.jdbc.base.BaseDriver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:525)
at java.sql.DriverManager.getConnection(DriverManager.java:171)
at com.stmxl.tools.DBHelper.getConnection(DBHelper.java:72)
at com.stmxl.dao.impl.tableinfo.SubjestQueryDaoImpl.queryMinOrganid(SubjestQueryDaoImpl.java:26)
at com.stmxl.service.impl.tableinfo.SubjestQueryServiceImpl.getThreeList(SubjestQueryServiceImpl.java:81)
at com.stmxl.action.tableinfo.ZtzxbmtzTableAction.initPage(ZtzxbmtzTableAction.java:56)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:399)
at com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:262)
at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:224)
at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:213)
at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:86)

因为本人对sqlServer不是很熟悉，请大家给予指教！谢谢