Trying to get a Rails app running on Snow Leopard.
Not had the experience myself and I'm using Snow Leopard, RVM and rails 2.3.5 to 3.0.3, but found another view which deals with the uninstall and reinstall via :
export ARCHFLAGS="-arch i386 -arch x86_64" ;sudo gem install --no-rdoc --no-ri -v=2.7 mysql -- --with-mysql-dir=/usr/local/mysql --with-mysql-config=/usr/local/mysql/bin/mysql_config
For more details see the posting at: http://accidentaltechnologist.com/apple/fixing-uninitialized-constant-mysqlcompatmysqlres-error-on-snow-leopard/