If you need to use this method, the SingleUser Mode performs some type of Database Check. It also informed me (by chance?) that the database had been terminated incorrectly (the power went down abruptly). It realigned everything and the problem was resolved.
1. I am running on Windows so. I opened a command prompt and was able to run the Single User startup from the Command Line
2. In the instructions be careful to locate on your machine which folders are correct (Postgres folder and Data folder). I am using Postgress with Alfresco obviously so the info in the instructions is varied slightly.
3. I will shortly be moving from a physical machine to a Virtual machine. This project originally started as a test, so we just installed on a standalone Windows 10 machine. In my case it would have been good to have the machine setup with some type of UPS and the problem would have been avoided altogether.
4. Make sure you have good backups - Even if this procedure had not worked I'm confident we could have brought Alfresco back up with the backups I kept.