DP 7.0 Network share backup not working

I'm trying to use the network share backup feature to backup files from a  NAS, but for every file DP logs this error, it's not a permission problem because can the permissions on the files are the same as the folders and it can see the content of every folder.

But why it tries to read at a negative offset ?

[Major] From: VBDA@server2011.server_2003 "\\server6\rete" Time: 29/05/2014 11.38.53
[81:78] UNC\server6\rete\log\ACQUA POTABILE\Foto mezzi nuovi\IMG_0008.JPG
Cannot read 20 bytes at offset -20(:2)