Premature end of script headers: wp-cron.php ? what to do?

Hi,

I am running WP-2.7.1. Since some days I am observing that my website is running very very slow. Even most of the time it gives me “503 Service Temporarily Unavailable”.
Some part of the day it work very well (w/o any problem) but in evening it again becomes very slow. Even the admin interface doesn’t open in such case.

While searching for cause I saw quite a lot “Premature end of script headers: wp-cron.php”, messages in error log.

Could this problem be because of wp-cron.

I am using dreamhost.

In wp_options table cron entry is like :
a:2:{i:1242955050;a:2:{s:17:”wp_update_plugins”;a:1:{s:32:”40cd750bba9870f18aada2478b24840a”;a:3:{s:8:”schedule”;s:10:”twicedaily”;s:4:”args”;a:0:{}s:8:”interval”;i:43200;}}s:16:”wp_update_themes”;a:1:{s:32:”40cd750bba9870f18aada2478b24840a”;a:3:{s:8:”schedule”;s:10:”twicedaily”;s:4:”args”;a:0:{}s:8:”interval”;i:43200;}}}s:7:”version”;i:2;}

website is at : http://buzz.nitinh.com

Please help me in debugging this problem.