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.
I haven't used it but if I were in your shoes, I would look at Bugzilla.
It is used by many open-source projects, which speaks to its utility, but also has the added benefit that once your team has learned it, then they are fluent in Bugzilla-speak and can track/post bugs in any open-source tools that you use.