Nonstop Backup/recovery from NAS with Errors

Hi There,

Acronis Home 2012 Update 2.1 (7133), Windows 7 32bit, no SP.
I´ve configured a non-stop backup to a NAS (External Western Digital Disk on Fritz!Box 7270 router).
Tried to browse the backed up files, but receive an error
0x01010005+0x01010005+0x01010009

I´ve removed the nonstop backup from the list and tried to re-add it by opening cdp.data, cdp.metadata or image.data, but received again error 0x01010005+0x01010005+0x01010009

The title of the backup has shown last successful backup a couple of month ago, but the logs have shown successful backups until today.
In the File System (Time explorer storage) it shows that image.data was modified today the last time. CDP.data was modified 3 weeks ago.

Something I´ve notices is that when I search a backup file I can see lock symbols on each of the folder on the NAS, but I don´t know what that means. I´ve also noticed that file attributes of the nonstop backup where write protected. So I went to the NAS, removed the write protections with the Windows explorer and tried to open the Acronis NS archive again withour success.

One more thing I like to mention is that the external WD-disk that is connected to the router has a standby mode , i.e. the HD will shut down if not used for 10 min. . If a process tries to access files on that disk, it will start up again and is available in the network. The start-up process takes a couple of seconds.

Update: I´ve just configured a new non-stop backup for a users folder  to the NAS and it works ok. So it doesn´t seem to be related to write protection or to the lock symbols

Thanks in advance for your help.
Hermann