When you did the work, did you remve the slide pins, clean and re-lube them?? Or did you just replace the pads and go? I had a noise VERY similar (which you could search for the post, but ultimately what I did/found below, fixed it)If I were you, I would do a FULL tear down, inspection and clean up... Take a look at this..
http://forums.genvibe.com/zerothread?id=30457Pads sometimes chip, espically if you pick up a rock or something... Would a lodged rock be a possibility? Lifetime pads are not the best idea, to be honest, they are HARD, they may last forever, but they also chew through rotors faster and make NOISE... lol.