Qt Creator won't stop at breakpoints

Hi, I’m debugging a Qt app. The project compiles, builds and runs properly however when I try to debug it I can’t get it to stop at breakpoints. I’ve tried building a test app using the Qt Creator Qt GUI Application template and in this case breakpoints work properly. I’ve tried cleaning and rebuilding to no avail. I’m using the “Start Debugging” button to start the process. I’m working on Mac OS X 10.8.2 and using Qt Creator 2.6.1 with Qt 5.0. Any suggestions as to what to look for? Cheers, Chris