Drupal's locale module includes a lot of great features for supporting multilingual sites. One such feature is the ability to associate a language with a path alias. This allows you to have one node with two versions, let's say an English version and a Spanish version. This permits each version to have its own alias.
But your use case may not require language-specific paths per node. Maybe you want to call a spade a spade-- you've got a Spanish node or and English node and that's it. No fancy multiple versions.
Well then you've got a bit of a problem--a few actually. This can wreak havoc with aliases, and pathauto in particular. So here's a snippet that essentially neuters Drupal's ability to assign different languages to paths: