MySQL Server has gone away:
http://dev.mysql.com/doc/refman/5.0/en/gone-away.html
Can be tricky to fix, but it's usually done in your my.cnf. You may need to increase the time out settings from the defaults or any of the many other options suggested at the URL above....then make sure to restart MySQL to load the new configuration. This is definitely a MySQL configuration issue.
I've also noticed a problem where some spammers IPs are listed on the SFS database who are able to register and post. We are still investigating that.