cannot run deltacopy client on one Windows Server 2003 - works fine on the other one

This is really bugging me. I have two servers on the same network behind the same firewall - one is an SBS2003 (call it server1) and the other is a standard Windows Server 2003 (call it server2).
DeltaCopy is running fine as a Client on server1, and is copying to an offsite WinXP SP2 setup as the DeltaCopy server.

On server2, I cannot get DeltaCopy client to connect to the same offsite WinXP - Unable to fetch directory names. rsync: failed to connect to xxx.xxx.xxx.xxx Connection timed out (116)

As a test, I ran the "Display Run Command", copied the command, and ran it from the command line.
(rsync.exe -v -rlt -z -u "/cygdrive/E/Backup/server2/" "user@xxx.xxx.xxx.xxx::Server2/server2/")
it issues this error message:
rsync: failed to connect to xxx.xxx.xxx.xxx: Connection timed out (116)
rsync error: error in socket IO (code 10) at /home/lapo/packaging/rsync-3.0.4-1/src/rsync-3.0.4/clientserver.c(122) [sender=3.0.4]

I have tried to reinstall from the exact same file, I have examined the ports using netstat, I have turned off the SymantecAV 10.2 (Symantec is running on both servers).

Any help would be appreciated.

Are you backing up to the offsite XP, with server1 and server2 at the same time?

I'm curious how many simultaneous backups the service can handle (if any).