Well, Shannon, I know from your first post you're asking for an expert/experienced opinion, but since no one has stepped in to answer your question I'd like to provide a couple of observations about the squeak issue.
First thing is this high-pitched sound during sensor cleaning is something that has gone on for years with Nikon and Canon cameras, and I can only assume with other manufacturers as well. People report the same observation you have, but to date I haven't read a definitive answer from either manufacturer. My take on this sound is that it is normal for the ultrasonic-type sensor cleaning that is performed by these cameras, and that not all cameras end up producing it and not all people's hearing is capable of hearing such high-pitched sound. Anyway, the sound is most likely produced by what's called intermodulation distortion when two or more frequencies in the ultrasonic range are producing a "spur" of sound in the sub-ultrasonic range. Do a Google search of intermodulation distortion if you want to read more on the subject.
Anyway, FWIW, I consider the sound to be normal and not damaging. Also, I fervently wish Canon and/or Nikon would address this issue with some kind of official statement in order to put this issue to rest.
