I ran across this when my Amazon Server seemed to crash out of the blue, after a restart I couldn't get MySQL to start.

A Nice Command for Debugging

1. Report on last 50 Errors in default System Log
   1. sudo tail -50 /var/log/syslog

What I eneded up doing was renaming the my.cnf file and letting MySQL regenerate it and it fixed it up.

1. sudo mv /etc/mysql/mycnf /etc/mysql/oldmy.cnf