OK, I've now determined that in my case, using a mid-2011 iMac and stock 10.9, a single active hardware network interface (built-in Airport Extreme, en1), running a newly-installed (post-10.9-installation) Xubuntu Linux 12.04 guest with guest additions and all default settings (no changes to the NetworkManager configuration), all network options on the VM work OK except the host-only interface. Any activation of vboxnet0 will cause the vampire VM to appear on shutdown. The NAT, Nat network, bridged, and internal options all allow normal shutdown. This includes the NAT network with IPv6 fully enabled and DHCP enabled. I do have real IPv6 connectivity on the hardware interface, in case it turns out that it matters. The only sharing service enabled in OS X is Remote Login (aka SSH). I wondered if there might be a problem with guests created before the move to 10.9, so I tried the same tests on a pre-existing Xubuntu 13.10 guest, and obtained the same results.
Hopefully this helps somebody out there decipher the problem or at least get a better handle on it.