Bootcamp can't erase with diskutility

I used bootcamp assitant to install Windows 8. In the installation of windows, I formatted the bootcamp part (because it says: "Windows cannot be install on this partition" anyway I formatted bootcamp partition to install windows in windows installation wizard. ) then I realize that I cannot choose startup partition disk. Obviously this is a problem. Also It hasn't got the name BOOTCAMP anymore. It named Untitled. I think because of that bootcamp assistant does not assist me anymore to remove this partition.

Here is my problem. When I am trying the remove that bootcamp partition in disk utility, I realize that every button on disk utility was greyed out! Thus, I cannot control disk partitions on diskutility. Then, I used recovery-hd for reaching advance setting in disk utility but same issue happend: every button greyed out. When I am trying to parttion my hard drive as one. It says "partition failed couldn't unmount disk".

I am frustrating any help will be appreciated.

Thanks

I have macbook pro retina 15'' 500gb SSD with mountain lion