My credit cards authorizations suddenly started failing, which I thought might be the result of me not upgrading - I had version 1.6.1. On upgrading to the latest stable version my admin backend is not accessible, all the site shows is Service Temporarily Unavailable.
I have a backup of the complete site so I can start over, and I do have ssh access now. I'd like to know the best place to start troubleshooting this type of error on upgrade. Any other answers on how to fix my problem appreciated.