My site has about 400 404s. Every time I use the plugin, I get through about 15 or so. Then it sort of "freezes." And then my website goes down for about 10 minutes...The whole page goes white and there is a small message in the top left that reads "error." http://www.51blocks.com.
I'm an SEO specialist and I use the plugin on many clients websites...it's only on my website that this happens, but I'm not of the cause.