Apparently everything was correct in my model, and it had been working smoothly so far. But suddenly the error "Unknown relation alias Translation" showed up.

After some research I found a very good explanation of the issue. The fix doesn't seem to be trivial, but after some more research I realized the problem indeed was trivial. In fact, I don't remember having wasted so long with such a stupid error.

I used the Symfony CRUD generator, and, when generating the code, it calls tables this way: Doctrine_Core::getTable('customer')->method()It always uses lowercase for the table names, but my model's name is actually "Customer". The lowercase mode seems to work in some cases, but it fails when there is a Translation relation.

Hope it helps.