You can try adding this to your functions.php file:
<?php
function my_formatter($content) {
$new_content="";
$pattern_full="{(\[raw\].*?\[/raw\])}is";
$pattern_contents="{\[raw\](.*?)\[/raw\]}is";
$pieces = preg_split($pattern_full, $content, -1, PREG_SPLIT_DELIM_CAPTURE);
foreach ($pieces as $piece) {
if (preg_match($pattern_contents, $piece, $matches)) {
$new_content .= $matches[1];
} else {
$new_content .= wptexturize(wpautop($piece));
}
}
return $new_content;
}
remove_filter('the_content', 'wpautop');
remove_filter('the_content', 'wptexturize');
add_filter('the_content', 'my_formatter', 99);
?>
Once you’ve added that and saved the file, you can wrap the code you don’t want formatted with a shortcode:
[raw]Unformatted code[/raw]
SOURCE:
http://www.wprecipes.com/disable-wordpress-automatic-formatting-on-posts-using-a-shortcode
NOTE:
I haven’t tested this solution, but it comes from a reliable source.