I had an issue the other day with AWS an Elastic Load Balancer (ELB) that said the instances I had assigned to the load balancer were "Out of Service". There was a link that was displayed as "(why?)", and would display the hint text of "Instance is in stopped state." This was particularly confusing, because the EC2 console displayed the instances as running.
It turns out that the problem was with the load balancer settings. Doing a search revealed that the error message "Instance is in stopped state." will be displayed when the health check fails. It turns out that the problem was that the health check ping target was pointing to the wrong location (a web page that didn't exist).
I wish that the AWS console would have listed a suggestion of "Please confirm that the health check ping target is correct." instead of just listing an invalid assumption that the instance was in a stopped state. Or, have the "(why?)" anchor display a page of possible troubleshooting steps. One of the suggested steps could still mention the possibility that the instance is stopped.
In the end it was resolved somewhat quickly, but it could have been a lot less stressful if the information provided was more accurate and more helpful.