As it was stated we can't re-open a previous issue that appeared to be the same, I'm starting a new issue.
Steps (on a clean install):
Install Mailchimp (7.9)
Install Libraries (7.2)
Add Mailchimp library to the libraries directory
Add Mailchimp API key
Trying to add a list creates a WSOD and error log says: [Wed Jan 16 16:48:22 2013] [error] [client 126.96.36.199] PHP Fatal error: Class 'MCAPI' not found in /var/www/vhosts/XXX/httpdocs/sites/all/modules/mailchimp/includes/mailchimp.inc on line 3, referer: XXX/admin/config/services/mailchimp/lists
/admin/reports/status page reports: The version of the MailChimp MCAPI library could not be detected.
Updated 3 sites yesterday and the same applies on update rendering the Mailchimp module completely unusable currently.