Whenever I publish article, site goes down for a few seconds.

I have set up a system on my front end that allows for users to submit content.

It is a multistep process that creates the post after the first step, but saves it as a draft. When they reach the final step, they click on publish, and by this time, all of the information has been added for the post, and the publish button changes the status to publish.

Weird thing is though, that when this happens, 1) it takes a VERY long time to submit, and 2) the site goes down completely for a brief time.

What could be factors that would cause this to occur?