I'm going to suggest two things that should help resolve this issue.
1. Under the Web UI > Properties > General you should find Network Sleep Settings or Sleep settings - disable them (The one for the network controller). I don't have the paperwork infront of me or a machine to look at but you should be able to find it there.
2. Contact the support center to obtain a firmware update for your machine.
in our office we have a xerox 5775
We have problems with scanning smb
the share folder where save the file is \ \ servername \ scan
These are the settings that I put:
hostname: servername : 139
login: MYDOMAIN \ user
but after several days stops working
I turn off and on the copier and it back to work ...