no backups in Redhad partition with many files and few changes.

hi!
we have a client who has one particon with many files and few changes. The backup of that particion is alwais wrong,we have not seen anything related to the "time outs". The error is:

client.name.com:/var lost connection to server, exiting

we have proven has to make backups with client firewall not actived (iptable stoped), the backup is made well.

when we change the client iptables rules, the backup is made well:

old rule : -A INPUT -m state --state NEW -p tcp -s X.X.X.X -j ACCEPT
new rule: -A INPUT -p tcp -s X.X.X.X -j ACCEPT

Normally, the rule is used is the first.
why does this change affect?
Does anyone know what happens?
is known that behavior?

thanks, and escuse me my bad English.

Arkaitz