I'm using two databases with two connections, one of these only in one component of the project.
I used Doctrine_Manager::bindComponent to set the connection for the tables of the second database, and left the main database's connection as default.
The bug happens when I'm using search() in a searchable table of the second database. Doctrine_Search::search function uses the default connection when queries the index table, instead of the connection bound to the searchable table.
I attached a patch, which works for me.