I finally figured out what's going on. I'm using the same machine as Guilhem Brouat was, the vagrant-win7-ie8 box. This box is not configured properly to be used by Vagrant, because the Modern.ie team released it before Windows was supported (I think?). Their goal was just to have a VM that could be spun up with "vagrant up" and then interacted with manually. It isn't set up to be accessed via SS