Cannot delete a contact

Cannot delete a contact

I have been de-duplicating some contacts as I'm importing from many different files.

I keep getting  notice every time I check the contact and use the "delete" button on my contact view screen. So I checked the box on the notice thinking it would stop showing when I tried to delete the next contact but instread it has now prevented me from deleting and contacts. It's like the delete button on my contact view has now been disabled.

Anyone come across this? So do I somehow need to switch the notice prompt on again?