We have recently developed a thumping or clunking noise in the wall when water is turned on or off in the lavatory sink (either hot or cold water). The clunk is also heard as the toilet stops filling. With each turn on/off, the clunk happens just once. Any idea what is causing this and what we can do to fix it? (The faucets, shower and toilet were all recentlyl replaced).

Sounds like your new valves are shutting off more abruptly and are causing water hammer. This only happens when something shuts off so I don't know where the noise is coming from if present when you turn on the faucet. Sioux makes several types of hammer arrestors you might want to consider. This is just one but search around their site. Sioux Chief Bullet for Residential Stub Out (http://www.jupiterheating.com/sioux-chief/adapters-bullet-residential-stub-out.html)