Updating series (i.e., adding one or a few episodes) is kind of tricky. Initially, there's no URL or actual title, so the IMDb search results are rather useless. TheTVDb plugin, however, always downloads all the available information for the series—so, if there is one, it will provide the episode name. With an episode name, the IMDb search will provide a reasonable search result (i.e., the target will be at or near the top of the list). So, I use a batch file that runs TheTVDb followed by the IMDb plugin. (Note that an IMDb search is likely necessary, so this has to be done with silent mode off.) If that doesn't work (e.g., TheTVDb doesn't yet have the episode title), the only alternative is to update the entire series—to get the episode titles and URL's—and then update the subject episode(s) again. That, of course, is a waste of time if there is no information there—often the case for recent episodes.
BTW—I suppose I should clarify—I'm not running two plugins in case one of them doesn't work. I run IMDb to get the credits, and TheTVDb for it's episode description.
(I expect to post a new release of PvdImport soon, btw. Did you have any luck with auto update?)
PVD is busy rebuilding my database (what I did before, but leaving the wish movies in). I'll try agian in 4-6 hours.