Window system driver installation failure kills `vagrant up`

I'm trying to use vagrant-vbguest to upgrade a VM provided by Opscode from guest additions 4.2.6 to the latest 4.2.8. As expected, I get an error when it tries to install the window system drivers, but unlike the project's README suggests, this causes `vagrant up` to abort with the message:

    The following SSH command responded with a non-zero exit status.
    Vagrant assumes that this means the command failed!

    /mnt/VBoxLinuxAdditions.run --nox11

If I follow this up with a `vagrant reload`, then Vagrant is unable to mount the shared folder via NFS:

    Mounting NFS shared folders failed. This is most often caused by the NFS
    client software not being installed on the guest machine. Please verify
    that the NFS client software is properly installed, and consult any resources
    specific to the linux distro you're using for more information on how to
    do this.

If it will help, here is the Vagrantfile on the shell session where I tried this: https://gist.github.com/jimmycuadra/5140125

Thanks!

Edit: The failure of NFS seems to be specific to CentOS. I tried a simple test with the official Ubuntu Precise 64 box from Vagrant, and `vagrant up` still dies with the same error when upgrading the guest additions, but the NFS mount works after `vagrant reload`ing.