doc_z - 6:46 am on Nov 2, 2012 (gmt 0)
I guess that the reason for the loss in ranking is not the plugin inself but the fact that there is a massive change in the internal links. (See this post. [webmasterworld.com]) I would simply wait and ensure that the "Related Posts" not change (which means that they are just generated once). However, when I'm right I take some time because Google first have to re-crawl the whole site and then see that the link structure is stable.