I had mysql running fine on OS X until I accidentally installed it via homebrew as well. I cant start mysql using preference pane and I cant login to phpmyadmin using my root password. Is there anything i can do?
I suggest uninstalling all occurrences of MySQL and reinstalling using just one method :).
I've seen some useful posts across Stack Exchange that explain how to remove MySQL, like this answer. Hopefully that can get you on the right path.