Something

$form['item'][$item->iid]['check'] = array(
		'#type' => 'checkbox',
		'#default_value' => 1,
		'#prefix' => "<div class=\"publish_checkbox\"",
		'#suffix' => "</div>",
		);

output: 
<input type="checkbox" name="check" id="edit-check" value="1"   class="form-checkbox" />

Checkbox isnt checked by default, but pass its state (0,1) as expected

Adding '#value' => 1

output:
<input type="checkbox" name="check" id="edit-check" value="1"  checked="checked"  class="form-checkbox" />

Checkbox is checked by default, but only outputs 1