I bet that, on the place you want to make a folder, you need Root rights. The dead giveaway:
Possible cause: the harddrive comes from annother system where the permission scheme is different. For example, you'd have a disk set up and running on Fedora, you'd set up a Linux (Arch, for example) on a different PC, add the disk to that PC and the rights/permissions would differ.
the contents of the drive, or approach the data as Root.