Another fast-google:
http://lists.samba.org/archive/samba-technical/2003-October/032249.html
I know that signing is working between the server and client at least initially, since I can successfully retrieve 750MB or so of data, and on shares that are smaller than that, I can get the entire share no problem. There seems to be something more insidious going on here.
You could also test if your backup works with "security = share" if your setup allows.
Good idea, just tried it, failed at the same spot. This is seeming more and more like a bug and less like a configuration issue. Maybe I should post to samba-technical....
-Fran
