Packets Drop After Ping

[RichCurl]

I have a Cisco 3750 and an HP 2910al connected together through a trunk link.  I have VLAN 308 and 309 defined in on both switches, with the cisco sharing that information with all the other cisco switches via VTP.  On the HP, it is statically configured.  On the HP, I also have setup a trunk group for a couple of NICs on a VMWare ESXi machine, which uses a Virtual Switch with an IP address of 10.30.8.51.  I can ping the IP from other devices across the WAN, for example 10.1.0.250.  However, once I ping the trunked group with the .51 address, from my Cisco switch (10.30.8.1), I can no longer ping it (.51) from any other hosts for a period of about 5 minutes.  Not sure where to look at what is causing problem...any ideas?