Hi,
first of all, it seems that you installed a package "virtualbox-4.1" in you box. Why is that? This package seems to be the VirtualBox _Host_ software (
http://packages.ubuntu.com/precise/virtualbox), not the GuestAdditions. You probably don't need this package and should remove it.
The hangs are either one of the common network-problems or a result of having a virtualizer inside your virtualized box. Try to boot the box in gui mode (`config.vm.boot_mode = :gui`) and look around whats going on. If the box comes up ok, you can log in with vagrant/vagrant and restart the networking interfaces (`sudo /etc/init.d/networking restart`) - this normally does the trick when network interfaces get confused.