Problem with OpenVPN

I built openvpn-2.0.7 on a Red Hat ES 4 machine. I can connect to it with the OpenVPN GUI from Windows laptops. I get authenticated, get an IP address, and get my routes from the VPN server. I can ping and ssh to the VPN server. I cannot ping or ssh to any other host on the same subnet as the VPN server. I can ping, but cannot ssh to, hosts that are behind a Red Hat 7.1 iptables firewall with an interface on the same subnet as the VPN server. I discovered I can ping that interface as well. I run tcpdump on the VPN server and grep for packets with the IP that my Windows machine gets from the VPN server. I see mostly traffic related to our AD server. I grep -v that traffic. Now, here's what's weird... I might do some pinging and ssh attempts. Nothing shows up in my tcpdump. But, several minutes later, some stuff appears. The lines are related to pinging and my ssh attempts. But not at a one-to-one ratio... a lot are just never seen. The pings from the Windows laptop to anything that responds are timely... ~20ms. I get all good responses, but, like I said, several minutes later, a couple of them might show up in the tcpdump I've been Googling, and turned up several mentions of "nothing showing up" in tcpdump for the tun0 interface on the VPN server. But nothing that says if that's OK or not, or what the cause fix might be. I'm stumped... what more can I do to get this working?

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