Hey Brian,
It seems like you don't have access to 10.1 SP1 AMIs. That's why you couldn't login to 10.1 SP1 Cloud Builder. In us-east region, the AMIs are called:
ami-19199370 Esri ArcGIS 10.1 SP1 for Server with SQL Server (Jan 2013)
ami-f319939a Esri ArcGIS 10.1 SP1 for Server with SQL Server Express (Jan 2013)
ami-96cb75ff Esri ArcGIS 10.1 SP1 for Server on Ubuntu with Postgresql (Oct 2012)
If you are still Esri customer, you should be able to get these AMIs since you have access to 10.1 Final AMIs. If you give me your AWS account#, I can check why you don't have access to 10.1 SP1 AMIs.
For 10.1 final Cloud Builder, since your account is touched by 10.1 SP1 Cloud Builder, you got the warning message. You will not be able to create site as well. But authorization shouldn't fail. Do you mind sending me your prvc file? I can check why that failed too.
Cloud Builder is designed not to go back to earlier versions. I would suggest going with 10.1 SP1 AMIs if we confirm you should have access to 10.1 SP1 AMIs. If not, we could also help you clean up your account and go back to 10.1 Final.
Thanks,
Cherry