Ghost 14 has stopped recognising my backup drive

My backups have recently stopped at around 95% (after some hours) and if Io go into "Manage backup destinations" and select my backup drive it says "This destination is currently unavailable - if this destination is an external device, make sure the device is connected and turned on. . If this destination is over a network.make sure you are logged in"

 

I am backing up to a Wetern digital external 1TB drive cionnected by firewire. It used to work fine wioth Ghost and I can access it fine through explorer. but Ghost seems to think it doesnt exist.

 

Any ideas? I cannot back up or access my data which rather defeats the object of a secure backup programme!

 

Philip