Errors after installing mysql
The problem I see is the error message that says


  Table 'mysql.plugin' doesn't exist 
  **120105  6:02:49 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it


MySQL 5.1 introduced plugins. MySQL 5.0 and prior do not have plugins. My guess is that you had MySQL 5.0 running, you uninstalled MySQL 5.0, and tried to install either MySQL 5.1 or 5.5 and it complained about mysql.plugin being missing.

Try cleaning up the 5.0 install as follows


uninstall mysql 5.0
Move /usr/local/var/mysql to /usr/local/var/mysql_old
Install mysql 5.5 


Give it a Try !!!