In the MySQL preferences, I have the "Automatically Start MySQL Server on Startup" selected, but MySQL doesn't start. Starting manually the server through the "Start MySQL Server" button works fine.
Any thought? Maybe wrong permissions?
It's a known problem that the preference pane is (was) broken in 10.6 Leopard. Try reinstalling just the preference pane, not the complete mysql package: http://dev.mysql.com/doc/mysql-macosx-excerpt/5.1/en/mysql-installation-macosx-prefpane.html