Why do posts not show for new blogs?

Hi,

Whenever a new blog is created within my WPMU site the posts don’t show up for a few days. It doesn’t matter if it is a new member or existing member that created the blog. Admittedly it comes in handy when a spam blog pops up because it will show on the main page, but if anyone clicks it just says “Sorry”. For real blogs it is rather annoying though.

Does anyone know why it acts in this way?

Thanks for any help,
Gene