USB Hard disk will not mount & causes system freeze

Hi, I have a USB external 1TB disc.
When I start it up the icon flashes up for a second then disappears, ie it looks like it is not mounted and I cannot use it.
If I turn the disc off manually it causes the system to freeze.
I am running xubuntu on a separate hard disc & don't see this issue.
Any help appreciated, thanks.
When I start it up the icon flashes up for a second then disappears, ie it looks like it is not mounted and I cannot use it.
If I turn the disc off manually it causes the system to freeze.
I am running xubuntu on a separate hard disc & don't see this issue.
Any help appreciated, thanks.