This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
If you haven't yet, check the log file (under the logs folder of your jakarta-tomcat-4.1 installation) catalina.out - if your error handler is writing to sys out, the messages will be there. See if you've exhausted memory. You may have a memory leak in your application and that may explain why your server seems to run most of the time.