Sorry but I came late to this discussion. If you are still open to
experimenting then I have another one for you. In the
/etc/network/interfaces file do you have the interface listed? Or is
it left to NetworkManager? If it is listed is it listed as
"allow-hotplug eth0"?
Try this. Change that to "auto eth0" instead.
that will change the startup from being event driven to being
synchronous at boot time.