I can ping from Server 1 on Subnet A, across the WAN, to Server 2 on Subnet B with no problems. Full response, no lost packets. But when I try to ping Server 2 on Subnet B from Server 3 on Subnet B, I get a reply on the first packet, then the rest time out.
At first I thought it was a Server 2008 thing, but I have the same issue trying to reach my Server 2003 box. I have replaced the switch, but I'm getting the same errors.