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.
Although the error message mentions threads, this really has nothing to do with threads, per se. You're simply running out of memory. WHatever you're doing once a minute is creating some number of objects, and at least some of them are being stored somewhere and not released. Examine your code for evidence of this.