@SpudR. Don't think reducing the threads is the solution.... I believe that putting in some sort of time out to the download request could potentially sort the issue. Will need to find some time to do some investigation in this respect.
things are getting weird. Just setting up an debugging environment, to see if I can help you a little figuring out where the problems lie.
With a clean MePo 1.8 Final install without TV-Server and DVD-Art is the only installed plugin my reported "Artist-Issue" is gone. It runs through all Artits without any stumble. Going to install all plugins now I have on my Livingroom HTPC, to see if they interfere with each other.
@Wise, go to settings and select what you want to use the plugin for by enabling the options from the scraping tab. Once you've selected what to scrape, reset the application by exiting and restarting.