I keep getting this error every once and a while on my local installation. I've never seen it on a live site. Maybe you could tell me why and if there's anything I can do to make it disappear.
Warning: fopen(http://localhost/3.0/wp-cron.php?doing_wp_cron) [function.fopen]: failed to open stream: HTTP request failed! in C:\xampplite\htdocs\3.0\wp-includes\class-http.php on line 1045