Error 404 On Log out and login

Hi,

I am getting an Error 404 on - http://drenalin.biz/staug/staug/?loggedout=true

This happens on log on and log in and doesn't seem to happen all the time. My client with a mac seems to get getting it consistently.

Wordpress - 3.3.1
Buddypress - 1.5.3.1
Membership Premium - Version 2.1.4

Any ideas?