The SEO plugin (got it on a regular install) isn't properly handling errors. Yesterday I did get "Cannot resolve host who.is", today I'm having a "curl_exec: connect() timed out" (see attachment).
It could be a slow DNS resolve. Try increasing the timeout in RankChecker.php from 5 to say 30. Look for the line that calls Piwik_Http::sendHttpRequest().
(In ) fixes #1479 - sendHttpRequest() can throw exception, so we must try...catch; also fix the formatting to conform to style guidelines; update third-party licensing doc