After my upgrade from Lucid to Precise (and thereby, from MySQL 5.1 to 5.5), I found that my MySQL instance was not running. When I tried to start the service all I got back was that it had failed to start.
I checked the system log (sudo tail /var/log/syslog) to see if I could divine the cause of this issue and I found the following messages:
init: mysql post-start process (5075) terminated with status 1
mysql respawning too fast, stopped