I just received this in my mail:
Hi,
For the last few months, we were working on a new monitoring engine that will work faster, better and scale.
We have it completed, ran lots of tests and, lately, activated it randomly for some accounts (including yours) to test its performance in the production environment.
It performs very good..except few issues that have ended up in several false/positives (including last night). Very sorry for them.
Waking you up with false/positives is the last thing we would want and, actually, we are here to make sure that you have a good/deep sleep knowing that your sites/servers are being watched.
We work so hard for that, have already applied multiple fixes and will be regularly improving the system to prevent such issues from occurring again.
Have a great weekend,
http://www.uptimerobot.com/
http://twitter.com/uptimerobot
It does explain allot why I was having repeated down times while all the servers where online.