I have never been able to get OpenID to work with Blogger. I'm on Yahoo hosting, trying to comment on Blogger blogs with my blog URL and it has never, ever worked.
However, the problem of the new WordPress version killing the old OpenID plugin may be related to whatever PHP version your webhost happens to be running.
It looks like (to me anyway) the new WordPress was designed to work on PHP 5 but the old OpenID plugin was designed for PHP 4. If you can get your webhost to run PHP 5 instead of PHP 4, then update your OpenID to 3.3.3, then everything should at least look like it runs happily.