I have the latest version of WP-OpenID (2.1.9) installed. I had been having some problems with an older version not letting me login with my identity url so I removed it but could never re-add it as WP-OpenID told me the nounce is already in use.
Today I upgraded to 2.1.9 but I still can't add the identity url. The same problem is reported. There is only one account on the site that has (or had rather) an openID identity Url associated with it.