Ok, here is my quest :
I would like to divide my loop on my category/index/archives templates.
I would simply put a banner between the first posts and the folowing posts.
First post in the loop
All the folowing posts
And I want to keep this schema over the pagination, ie when I browse the older posts in category/archive/etc.
Normally, I would do so with :
 A query posts with showposts=1 = Display only one posts.
 The banner I want to display
 A query posts with offset=1 = Display all folowing posts.
But this method wont works with the pagination to browse older posts.
I know how to get the pagination working with a single query_posts, with this code :
$page = (get_query_var('paged')) ? get_query_var('paged') : 1;
But it doesn't seems to solve my actual problem with two loops...
Am I clear enough? Anybody have an idea?