Odd one-way ping issue that I can't wrap my head around

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http://serverfault.com – Long time lurker, but today I encountered an odd problem that will bug me until resolution :-) It seems to be presenting as a one-way ping issue from one server to a failover cluster. All machines are running Windows Server 2008 R2 with IPV6 disabled. The windows firewall service is disabled. Lay of the land: Report Server - VMWare Virtual Machine using E1000 NIC. Nothing special - IP, Subnet, Gateway and routing table all appear sane. SQL 2008R2 Active/Passive Failover cluster - Each has 7 configured NICs- 3 iSCSI, and the remaining 4 bound to 2 IPs with BACS. One NIC Team is used for (HowTos)