I don't know if my problem (IS250) is the same as yours but I get quite loud "cracking" noises from the front when manoevering at low speeds - i.e. in or out of a parking space.
My local garage has fixed the problem once and explained that the ?brake shims? become degreased and stick and it's these freeing themselves that make the cracking.
The last time they re-greased the offending items it worked for about 6 months but has started again and I am taking my car for a check this evening
as it is quite off putting!
