You can recover your /etc/passwd file from your shadow file which most likely shouldn't have been affected if the issue you ran into was related directly to /etc/passwd.

Here is a great article on this:
http://www.cyberciti.biz/tips/recovering-deleted-etcshadow-password-file.html

We're looking to make a bit more progress in the next 2-3 weeks after our new control panel is released to provide new features to customers, one of which will be to boot a recovery ISO. This will then allow you to mount your virtual servers disk there and make any necessary changes if it has got to the point where you are unable to boot it directly.