I've never seen this error message before. I get it randomly - sometimes when I'm trying to access a page on the site and sometimes when I'm trying to access a dashboard page. The site is currently in development. I'm unsure how to find the culprit.
I'm seeing this too - I'm with Bluehost and after about 10+ support calls, they refuse to accept that its a server issue and keep telling me to optimize my (not very heavy or large) site. I have no idea what to do on my end to mitigate this. It seems to happen during certain parts of the day which does seem very much like a server issue.
You are allowed to delete your post for 5 minutes after it's posted.