During my first week of setting up vagrant, got this weird error when running
vagrant up. After some research on the internet, it turns out that the issue is caused by my VirtualBox version. Downgrading seems to be the best option.
I used the latest Vagrant version but at first, I used the latest VirtualBox version to date. That was VirtualBox 4.3.14 or something. According to forum posts, VirtualBox 4.3.12 seems to be working. So I downgraded VirtualBox to 4.3.12.
Everything is working now so far.
Enjoy and share.