Witnessed the same thing. Restarted the database server and the errors seem to have gone away.
I think it's just because the database server hasn't seen the web servers performing this well before and hiccuped.
Normally, with this level of traffic, the webservers would have start responding slowly, and not have stressed the database as much. Now that the webservers are snappy during periods of high traffic, the database crapped out.
I'm looking into what I can do to increase db performance.
It's slow for me almost nightly. Not a database error, just like a lag. Often I've noticed on the bottom of my browser it will show "waiting on vshare" or some variation of that, and it gets annoying. I love this site and want to spend more time on here, but the hangups drive my crazy.