Because of a suspected bug in the mysql gem on the Mac,
I cannot perform simple rake commands; for example, 
rake db:migrate --trace
(in /Users/rickcasey/Projects/ror/expenses)
** Invoke db:migrate (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:migrate
rake aborted!
uninitialized constant MysqlCompat::MysqlRes
/usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:440:in `load_missing_constant'
/usr/local/lib/ruby/gems/1.8/gems/activesupport-2.3.5/lib/active_support/dependencies.rb:80:in `const_missing'
.... 


This bug in the mysql Ruby Gem has been a severe and baffling problem for many; e.g. see the litany at 
http://stackoverflow.com/questions/1946182/problem-installing-mysql-gem-on-snow-leopard-uninitialized-constant-mysqlcomp
at

Googling the simple error message: 
"rake aborted!
uninitialized constant MysqlCompat::MysqlRes"

will show many others suffering from this bug. 
Please help!