If you use Windows 7 File Recovery to attempt to backup your system to a NAS device, you may receive the following error:
The specified network location cannot be used.
Verify the path points to a correct network location and that the supplied credentials can be used for write access to the folder.
The validation information class requested was invalid. (0x80070544).
The solution to this is rather simple. You have to prefix your username with the name of the machine where the Samba share is located. So, if you are backing up to diskstationbackups, prefix your username with diskstation.
In my case, my username on that device is mike. So instead of using mike as my username, I had to use diskstationmike.
It works now. Enough said.