Is there anything in the error log? What about deleting the device and recreating it?

-Mike

>Error is :
>
>Can't open dump device 'D:\Mssql\...\DeviceFile.DAT', device error or device off line (Message 3201).
>
>
>That device is on a disk, not on a tape.
>Service pack 5a is installed.
>A manual back-up on the same device works well.
>This device is not used by any other task.