unline asamuels this is the first successful find for me regarding this subject. Thanks for your solution, filosofo. I wanted the simpler version, the existing posts_per_page value (from the options) on the index page, but in a specific category I wanted all posts.
In order to apply your solution to my code, I need to set a very high number, such as:
$GLOBALS['wp_query']->query_vars['posts_per_page'] = 1000;
query_posts($GLOBALS['wp_query']->query_vars);
//now we're going into the loop
using -1 or ‘-1’ returns nothing. Not a problem for me this time, but is there an explanation for this, for posteriority? And could this be solved using filters/actions instead of putting the code into the template?