[Plugin: Yet Another Related Posts Plugin] Fatal Error During Latest Upgrade

YARPP was working very well. However, after automatically upgrading YARPP, I receive the following error after failed attempt to activate plugin:

“Plugin could not be activated because it triggered a fatal error.

Fatal error: Call to a member function is_enabled() on a non-object in ../httpdocs/wp-content/plugins/yet-another-related-posts-plugin/includes.php on line 68″

– I have uninstalled and reinstalled.
– I have attempted to install and activate version 3.2.1b4 & 3.2.2 files from forums.
– Check box is Disqus commenting is checked.
– I disabled Disqus, WordPress SEO and a few other plugins that were recently changed. However, error persists.

Is anyone else seeing this, and could you please offer any advise for correction?

Thanks in advance.