I have used both that the others work on and also another one on a usb hub connected to the pc
Seeing as how it works on another computer, indicates the device is not faulty, so possibly there are too many USB devices attached, drawing power from the Hub. Have you tried disconnecting other USB devices b/4 plugging it in ? Did you ever have any files on it, ie, is it formatted with acceptable file system ? Did the other computer use same OS ?
No there is 1 item on a 4 hub in use and I have 4 ports on the pc - 2 in front and 2 at rear. I have tried all that you suggest so far aswell. I put 1 file on it on my other pc to test that theory too. I use Vista on this pc and the other has XP.