When Virtualbox is installed on linux and VMs created with networking using the host-only adapter to communicate with each other, it has been discovered that after the host wakes up from sleep, the host-only adapter appears to be UP on the host, however the VMs cannot ping each other.
This script, kickHostAdapter, can be placed in any directory that is part of PATH and run when you encounter the issue.
The script uses VBoxManage to get a list of host-only interfaces, then finds the VMs using it, then sets the interface off, then on for each.