I own an 06 Murano and had the same damn problem.
Took it to different dealers and tried looking online for any info but no go.
Anyways my car came back from the dealer today and they told me there's a bullitten out for it. I though I'd post it here since I love the car but the brake problem was driving me nuts. I hope this helps some of you out so you don't have to go through what I did. Cuz taking the car to different dealers and thinking it was fixed, then squeak the day after was a bit frustrating.
BULLITTEN NTB07-012"Squeal / Squeak noise from the front brakes when backing up with cold brakes"
Only online reference I found was here:
http://www.nissantechinfo.com/...07012