服务器老出现这种错误，怎么办？

tomcat5.5.17root cause java.sql.SQLException: Network error IOException: Socket is not  connected: connect
net.sourceforge.jtds.jdbc.ConnectionJDBC2.<init> (ConnectionJDBC2.java:372)
net.sourceforge.jtds.jdbc.ConnectionJDBC3.<init> (ConnectionJDBC3.java:50)
net.sourceforge.jtds.jdbc.Driver.connect(Driver.java:178)
java.sql.DriverManager.getConnection(Unknown Source)
java.sql.DriverManager.getConnection(Unknown Source)
org.apache.jsp.bbs.bbs.main_jsp._jspService(main_jsp.java:70)
org.apache.jasper.runtime.HttpJspBase.service (HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service (JspServletWrapper.java:332)
org.apache.jasper.servlet.JspServlet.serviceJspFile (JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service (JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)