IGMP Snooping is definitely disabled:
sw6#sho ip igmp interface vlan 1
Vlan1 is up, line protocol is up
Internet address is 172.16.x.x/24
IGMP is disabled on interface
Multicast routing is disabled on interface
Multicast TTL threshold is 0
No multicast groups joined by this system
I uninstalled vShield Data Security from hostB (since it wasn't installed on hostA) and reinstalled the vShield Endpoint on hostB. I'm not sure which change fixed it, but I can now get an IP address and ping the Edge from a VM on hostB when the Edge is on hostA. I'm back to where I was a while ago, a problem we thought we fixed. The VM can get an IP, ping, perform DNS lookups, but the browser won't connect to any websites (or connects intermittently, or to only certain sites; Bing seems to work consistently). VMs on hostA work without any issue. Could IGMP be the root cause for all of this?