All sorted followed the advice here https://discussions.apple.com/thread/4091299?start=0&tstart=0
I did this. It went away.
Terminal:
diskutil list
Find for the disk you want to format disk0, disk1, disk2,...
Disk 0 is usually the one you are booting your os x so dont use that
I closed all mounted virtual volumes
name: partition name
JHFS+: format type
diskutil eraseDisk JHFS+ name disk2
Yes, i should have known. Kicking myself now!