My entire bathroom was gutted and renovated in Dec. 2011. Water is coming down through the kitchen ceiling below the tub, but only when taking a bath - not at all when using the shower. All the pipes/plumbing is new since the tub and faucet is all new. The contractor has come back three times and found somehow the tub faucet is coming loose from the tile wall, and he thinks that is causing the leak. Each time, he has put more and more sealer of some type. Is it possible a loose faucet could be causing water to run down through the kitchen acoustic tile? Or is it more likely a possible overflow type problem?

Your contract is a hack and appears clueless on how to fix this issue. Faucets are attached to studs, walls are attached to studs. A leaking shower valve or divereter can send water almost anywhere.