I purchased my 09 CTS-V on Jan 2, 2009. In June 09 I noticed a popping/clicking sound coming from the front/passenger side. Dealer removed wheel, cleaned rotor, wheel, etc. and sound disappeared. In Sep 09, a similar but louder sound started in the driver/front side - especially during turns at slower speeds. Dealer replaced front left rotor assembly - seemed to fix the problem. In Dec 09, both driver and passenger/front popping sound started during reverse out of parking space (left and right reversals). Dealer was able to replicate consistently but determined this to be 'normal condition for a limited slip differential as compared with another, like CTS-V" on the lot. Today (Jan 7, 2010), the front end pops loudly and the front end of the car 'hops' when reversing out of a parking space -- every time. I contacted my dealer on Jan 6 stating the condition is unacceptable and requires further communication with GM engineering.