Orderby title doesn't sort numbers correctly

Titles sorted in the alphabetical order that is different with numeric. May be you need to order posts by a custom field value, by using the 'meta_value_num' orderby parameter in the query. The Codex tip

Here is a bit of code that shows how to sort the posts array in the manner you described:

// Test leading numeric title sort
query_posts("posts_per_page=-1&caller_get_posts=1&orderby=title&order=ASC&cat=97");
if (have_posts()) {
   usort($wp_query->posts,'my_post_sort');
   while (have_posts()) {
      the_post();
      echo "<br />";the_title();
   }
}
function my_post_sort($a,$b) {
   $akey = $a->post_title;
   if (preg_match('/^(\d+) /',$akey,$matches)) {
      $akey = sprintf('%010d ',$matches[0]) . $akey;
   }
   $bkey = $b->post_title;
   if (preg_match('/^(\d+) /',$bkey,$matches)) {
      $bkey = sprintf('%010d ',$matches[0]) . $bkey;
   }
   if ($akey == $bkey) {
      return 0;
   }
   return ($akey < $bkey) ? -1 : 1;
}

That is odd, it works for me. Here is the result of my test of the code:

Sorted by title
1 number test
100 number test
20 number test
45 testing again
another number test with no number
number test without number

After numeric sort
1 number test
20 number test
45 testing again
100 number test
another number test with no number
number test without number

Are your post titles entirely numbers – no text after the number?

That is not what you showed in your original post, so the preg_match is not quite right. Change the preg_match patterns from this:

(preg_match('/^(\d+) /', . . .

to this:

(preg_match('/^(\d+)/', . . .

by taking out the one space before the trailing slash.

Just a guess, but try adding $wp_query to your globals.

Here is the exact code I used (I added some debugging code).

Here is a screenshot of the results.

Did you add in the debug code?

Did you show all the output above? If so, the sort routine is not being called because the debug info is not shown.