We have two early 2009 xserves that we updated to 10.8.2 (Server or client, both behave the same). We then put Fusion 5.0.2 on them. Now when there is a Windows 2008 R2 guest on the machine, we have about 50% packet loss when trying to ping the VM from a different physical machine.
If I ping the machine from the host, everything is fine.
I moved the VM to another early 2009 xserve running OS X Server 10.6.8 and Fusion 5.0.2 and there are no problems pinging the guest.
We are doing bridged networking with Autodetect. I have also tried changing that to use Ethernet 1 or Ethernet 2, but both had the same problem.
On the 10.8.2 servers, I tried restoring from the restore partition and doing a clean install, but still has the same effect.
Anyone have any ideas? Please let me know if you need more information.