rake db:data:load gets stuck on Linux but not on OS X?!?

[gamov]

When I load data with db:data:load on OS X with same version of ruby/rails/mysql, it works but when I do the same on Ubuntu it gets stuck after a while (mysqld and ruby stop using CPU time after a while).
Each time I cancel the task with --trace, it is waiting on:

 .../vendor/bundle/ruby/1.9.1/gems/activerecord-4.0.13/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:287:in `query'

I really wonder where should I look for a potential fix?
I love this gem, very elegant to migrate data from one database to another.