When a volunteer reports a problem, respond to it right away. Sometimes, the problem is that no one other than Jenn feels that she has the responsibility to take care of a problem, so the first thing to think about is whether to give the reporter the authority to fix the problem herself. If it really is the coordinator's responsibility, investigate the problem and fix it - right away. An unfixed problem is a little like an open source program that doesn't compile - the longer it doesn't work, the more volunteers drift away. Responding immediately also reassures the group that you care about the project.