After upgrading to the new version of the plugin released a few days ago using the automatic upgrade process, I was asked to re-enter my API key. When I did so, I got the message that the key was associated with another self-hosted blog and I could add a new blog or replace an old one and inherit its stats.
I can't imagine why my key wasn't preserved in my options, but I presume that replacing the old blog and inheriting its stats is the way I want to go here. However, there doesn't seem to be a way to do it. When I click the given link, my "new" blog is added and my stats apparently start over from zero.
What is going on here? How should one upgrade the plugin without losing previously collected stats?