This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
One of your threads is getting STUCK. Weblogic marks threads in the STUCK state when it does not finish within 10 minutes (this time is configurable). If you have a debugger like eclipse you can use that to analyze which app thread is getting stuck and what it is doing.