I have a self hosted blog but now the WordPress.com stats plugin has stopped working

I’ve got a self hosted blog and yesterday (18th March) the stats package stopped working. I’m getting the message:

Your WordPress.com account, [account] is not authorized to view the stats of this blog.

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where [account] is the name of my WordPress.com account.

I deleted and reinstalled the plugin’s package and got the following message when I entered my API key:

The API key “[apikey]” belongs to the WordPress.com account “[account]”. If you want to use a different account, please enter the correct API key.

Note: the API key you use determines who will be registered as the “owner” of this blog in the WordPress.com database. Please choose your key accordingly. Do not use a temporary key.

The recommended action is to “Recover stats”

The other choice is to recover the stats of my blog.

However, what ever I do results in the same error.

If I log into WordPress.com with [account] I get an error message:

You are not a member of this site.

This is the only account I have registered with WordPress.com.

How do I link my blog back to WordPress.com?

I should add that I’m am running WordPress 3.1.