Trouble with save files

[jossmetal]

I started playing a new campaign and when I wanted to save progress the game couldn´t create a save file, delete an old one or even save over an existing file, it always says that there is a problem with disk space or something like that.
Other than that there are no other problems with the game.
I run the game in my portable hard drive that I exclusively use for games, as far as I know, no other game has trouble saving and loading from that hard drive, so I don´t think the hard drive's hardware is the issue; also the game is updated as far as I'm aware.
Does anybody has had similar issues??