There are reports coming in that sites that didn't work before suddenly started working again.
This makes me believe it's something more as wp-blog-header.php has been compromised.
I would love to receive a zipped up WordPress blog of a site that didn't work and suddenly started working again, wp-config.php can be omitted (No need to see your password :) ) to see if I can find out what else is compromised, how this started and see if I can come up with a solution.
If anybody is willing to send me a zip file shoot me an email @gmail.com my user is pvanderdoes