An error occurred: 1. Ditto: can’t get real path for source

Hi,
While working on my system last night I encountered with this error suddenly and I was unable to access my hard drive anymore. Don’t know what exactly happened.
Can anyone tell me what should have happened and how to resolve this issue?
Thanks.

The disk could not be created because of an error:
An error occurred: 1. Ditto: can’t get real path for source
