Not sure this is applicable to your situation, but I somehow got mine resolved.
I tried to manually install Windows 8.1 with bootcamp and it failed to auto install, so I manually partitioned some free space with disk utility. After I tried to install windows again the setup created this evil "disk0s4" partition that is protected with no user privilege to modify or remove.
I attempted many resolutions suggested on the web but none of them worked, then I thought to myself, if this partition was created by the MS windows installation boot disk would that be the place to remove it? So I ran the Windows setup procedures again (inserting the disk/bootable usb, and hold option when boot, then select "windows" or "windows setup" or however you name your installation source). When I reached the part where I can select which partition to install, I then delete the "disk0s4" partition from there. Restart your mac, launch disk utility again and its gone!
- Insert OS installation disk/USB (Windows 8.1 for me)
- Boot holding option and select the source (Windows on a USB for me)
- Proceed with installation till you hit the part with several
- Select and delete the "disk0s4"
- Remove the installation medium and reboot
- Launch disk utility again and it should be gone!
Hopefully this helps!