>>1744580not sure why everyone is being so hard on me, as if they've never had mechanical trouble, but whatever. derailleur is in good adjustment, wheel was true before today. problem is that the spokes come so close to the extrusions on the back of the cassette that it may be impossible to keep them from touching under certain circumstances. pic related, there's not even a mm of room between cassette and spoke. unfortunately one of the spokes has been knocked loose. will just take the wheel to the fellow who built it, see what he has to say.