Updating a module for D6: submit handler ignored

I'm trying to update my module for D^ and now for some reason, my module's submit handler function is being ignored. After I click submit, the page basically reloads. I'm not sure why this is the case.

<?php
function InventoryChecker_help($section='') 
{

	$output = '';
	switch ($section) 
	{
		case "admin/help#InventoryChecker":
		$output = '<p>'.  t("Cancel online Listings that are no longer in stock") . '</p>';
		break;
	}
	return $output;
} 

function InventoryChecker_perm()
{
	return array('access InventoryChecker content');
}

function checker_form($form_values = NULL)
{	
	$form['header'] = array
	(
		'#type' => 'value',
		'#value' => array
		(
			array('data' => t('ItemID')),
			array('data' => t('Title')),
			array('data' => t('End?')),
		)
	);

	$online = Get_Online_Listigs();
	
	foreach ($online as $key => $value)
	{
		$form['Items'][$key] = array
		(
			'#type' => 'markup', 
			'#value' => check_plain($key)
		);
		$form['Titles'][$key] = array
		(
			'#type' => 'markup', 
			'#value' => check_plain($value[Title])
		);
		$form['End'][$key] = array
		(
			'#type' => 'checkbox',
			'#return_value' => $key,
		);
	}
	$form['submit'] = array
	(
		'#type' => 'submit', 
		'#value' => 'End',
	);

	//$form['#validate'][] = 'checker_validate';
	$form['#theme'] = 'checker_form';
	
	return $form;
}

function theme_checker_form($form)
{

	foreach (element_children($form['Items']) as $key)
	{
		$row = array();
		$row['data'][1] = drupal_render($form['Items'][$key]);
		$row['data'][2] = drupal_render($form['Titles'][$key]);
		$row['data'][3] = drupal_render($form['End'][$key]);
		$rows[] = $row;
	}
	$output = theme('table', $form['header']['#value'], $rows);
	
	$output .= drupal_render($form['submit']);

	
	return $output;
}

function InventoryChecker_theme() 
{
	return array
	(
		'checker_form' => array
		(
			'arguments' => array('form' => NULL)
		),
	);
}

function checker_form_submit($form_id, &$form_state) 
{
	echo "GOT HERE!"
	return;
}

function InventoryChecker_block($op = 'list', $delta = 0, $edit = array()) 
{
// listing of blocks, such as on the admin/block page

	switch ($op) 
	{
		case 'list':
			$block[0]["info"] = t('Inventory Checker');
			return $block;
		case 'configure':
			return '$block';
		case 'view': default:
			$block['subject'] = 'InventoryChecker';
			$block['content'] = drupal_get_form('checker_form');
			return $block;
	}
}
?>

Any help is much appreciated.