Contact us module

Hi every body, I am developing a custom contact us module. I have already build a info file and a template file along with this module. I have also enabled this module from the module list section. Now i have a problem while theming this form. The form is displayed at "contactme/contact" url, But the the function contactme_form_theme is not called also the tpl file is not called.I also tried changing the theme function name as hook_theme this too failed. Can you please help me solve this problem and suggest me how to theme a custom form module.

I also tried to call the theme function from the hook_form function as return theme_contactme_form($form). but i got the following error:

Fatal error: Cannot use string offset as an array in C:\xampp\htdocs\drupal-dev\includes\form.inc on line 984

<?php
// $Id$
/**
* @file
* Module for contactme form.
* This module provides block form for contactme
* **/

/**
* Implementation of hook_block()
*/
function contactme_help($path, $arg){
    switch ($path) {
        case "admin/help/contactme_help":
        $output = '<p>'.  t("contactme is a contact module for contactme") .'</p>';
            break;
    }
    return $output;
} // function contactme_help

/**
* Valid permissions for this module
* @return array An array of valid permissions for the contactme module
*/
function contactme_perm(){
   return array('administer contactme', 'access contactme contact us form');
} // function contactme_perm()

/**
* Menu for this module
* @return array An array with this module's settings.
*/
function contactme_menu(){
	$items['contactme/contact'] = array(
    'title' => 'Contact contactme',
    'page callback' => 'contactme_message',
    'access arguments' => array('Contact contactme'),
    'type' => MENU_LOCAL_TASK
    );
    return $items;
}

/**
* Test Module Messages
* @return array An array of form data.
*/
function contactme_message(){
    return drupal_get_form('contactme_form');
}

/**
* The callback function (form constructor) that creates the HTML form for contactme_message().
* @return form an array of form data.
*/
function contactme_form(){
	$form['product_demo'] = array(
	'#type' => 'checkbox',
	'#title' => t('Yes, I would like to view demo.'),
	'#default_value' => '',
	);
	
	$form['first_name'] = array(
	'#type' => 'textfield',
	'#title' => t('First Name'),
    '#size' => 30,
    '#maxlength' => 64,
	);
	
	$form['last_name'] = array(
	'#type' => 'textfield',
	'#title' => t('Last Name'),
    '#size' => 30,
    '#maxlength' => 64,
	);

	$form['email'] = array(
	'#type' => 'textfield',
	'#title' => t('Email'),
    '#size' => 30,
    '#maxlength' => 64,
	);

	$form['company'] = array(
	'#type' => 'textfield',
	'#title' => t('Company'),
    '#size' => 30,
    '#maxlength' => 64,
	);
	
	$period = array(0=>"Select One","a"=>"a","b"=>"b","c"=>"c","d"=>"d","e"=>"e","f"=>"f","g"=>"g","h"=>"h","i"=>"i");
  	$form['market'] = array(
    '#type' => 'select',
    '#title' => t('Market'),
    '#default_value' =>'',
    '#options' => $period,
    //'#description' => t('The timer.'),
  	);

	$form['title'] = array(
	'#type' => 'textfield',
	'#title' => t('Title'),
    '#size' => 30,
    '#maxlength' => 64,
	);

	$form['message'] = array(
	'#type' => 'textarea',
	'#title' => t('Message'),
	'#default_value' => variable_get('message', ''),
	'#cols' => 50,
	'#rows' => 5,
	'#description' => t(""),
	);
   
    //Submit button:
    $form['submit'] = array(
        '#type' => 'submit',
        '#value' => t('Submit'),
    );
    return $form;
}

/**
 * Theme function for the contactme form.
*/
function theme_contactme_form($form){
	return array(
    'contactme-template' => array(
      'arguments' => array('product_demo'=>NULL),
      'template' => 'contactme-template'
    ),
  	);
}

/**
* Form validation for this module's settings
* @param form an array that contains this module's settings
* @param form_state an array that contains this module's settings
*/
function contactme_form_validate($form, &$form_state){
}

/**
* Form submission for user data.
* @param form an array that contains user data
* @param form_state an array that contains user data
*/
function contactme_form_submit($form, &$form_state){
}