Our friends at Litmus issued this alert:
Unfortunately, we are currently experiencing some database issues and testing will be unavailable until we have them fixed.
We are currently swapping to our back up database , and things should be up and running again within a few hours.
If possible, you may want to notify your users so fewer tests are started while the system is completely down. We are of course working flat out to get things back up.
We are really sorry for any disruption this will cause you and your users.
Follow our twitter @litmusapp for status updates about the problem.
Having just sent out the update regarding our problems, the clever folks behind the scenes here at Litmus have fixed our database problem and we are back up and running smoothly again.
Apparently we were subject to an obscure Mysql bug. Gladly we weren't down for long and hopefully disruption was minimal to you and your users.