BootCamp can't partition
I recommend the following:


Boot to Recovery HD by pressing cmdR while starting your Mac, open Disk Utility and first check the superior disk, then inferior volume for errors and repair them if necessary.
Boot to single user mode by pressing cmdS while starting your Mac and enter fsck -fy. If you get a message stating ""FILE SYSTEM WAS MODIFIED", reenter fsck -fy until you get the message "The volume … appears to be OK". Then enter reboot.
If you still can't reinstall Windows with Boot Camp Assistant consider rebuilding the GUID partition table.