TI Home 11 and WD My Book Live 3TG NAS drive?

So far I used TI Home 11 to backup my stuff on external USB or eSATA disks and it worked well.

Know I've got a NAS drive, a 3 TB WD My Book Live, and hope I could use this as well. The drive works well on my Windows Vista Home Premium equipped laptop. But when I try to make a backup with TI 11 it claims this network drive would not be connected and thus cannot be used. That's for the mount I did with a proper drive letter. If I try to use the drive as it shows up in network neighborhood TI claims that access credentials would be wrong. But actually I have not set any access credentials (user name & password).

What's wrong? And how can I fix this and make TI work with my NAS?

FRAC