When that happens with my Arroyo, my LBS tightens the chain. It only seems to last a while before it gets noisy again. I bet my LBS will recommend replacing the chain the next time I have my bike serviced. I have ~2000 miles on my Arroyo, so I suspect the chain is somewhat worn/stretched. I plan to take it in for a tune-up sometime this winter, so it will be interesting to see what the LBS recommends.