Update as of 21:00 p.m. UTC: The root cause of this issue was identified as a code change made to the Pardot application. This change has been reverted by deploying previous code. Login and performance issues have been resolved and full service has been restored. Please contact Support at http://success.pardot.com
if you encounter any further issues. We sincerely regret any inconvenience you have experienced as a result of this incident.