Daniele Riefoli - 2014-02-09

Hi to all.
I have a problem during a backup by 7z.exe batch command.
My OS is Windows 2012 Essential 64 Bit
7zip version 9.20 64bit

After compressing 300 files about , return the following error:
System error:
Impossibile trovare il file specificato.

the file it refers is really existing.
The batch command is:

set solita=%date%
set nuova=%solita:/=%
set dinuovo=%nuova: =
%
7z.exe a d:\dati%dinuovo% x:\e >7zip.log

What is the problem ?
Thanks
Daniele