Get a list of all enabled block deltas I need an array of all enabled blocks' deltas.

For example, if I display the array, it should output the block deltas e.g. search_form, user_new, user_login, and not the block titles e.g Search, User etc

I've found a few candidates:
http://api.drupal.org/api/drupal/modules!block!block.module/function/block_list/7

http://drupalcontrib.org/api/drupal/drupal%21modules%21block%21block.module/function/block_get_blocks_by_region/7

But they all crash my site. Really can't get it to work, please give some examples that works for you.
I can't imagine why your site is crashing using the two functions you link to (Drupal calls them both internally so it certainly shouldn't be), but you can use the following custom query to grab that data directly from the database:

$query = db_select('block', 'b')
  -&gt;condition('theme', $your_theme_name)
  -&gt;condition('status', 1)
  -&gt;condition('region', -1, '&lt;&gt;');

$query-&gt;addExpression("CONCAT(module, '_', delta)", 'delta');

$deltas = $query-&gt;execute()-&gt;fetchCol();

// $deltas now contains a list of deltas for all enabled blocks in the provided theme