For some reason I had some problems getting my MySQL homebrew installation working: Error 1:

"FATAL ERROR: Could not find ./bin/my_print_defaults"

Fix for Error 1 (hopefully) :

unset TMPDIR
mysql_install_db

Error 2:

FATAL ERROR: Could not find ./bin/my_print_defaults

Fix for Error 2:

unset TMPDIR
mysql_install_db --verbose --user=`whoami` --basedir="$(brew --prefix mysql)" --datadir=/usr/local/var/mysql --tmpdir=/tmp

And hopefully that will fix your MySQL :/ I just happened to find the above on the net, so I doubt I can be of much help if that doesn't work, just thought I'd post it.