creating custom plugin that uses media uploader

11-month-old post atm, but here’s your answer:

Did you conditionally add your upload script based on the $_GET[page] variable? From, the link you posted they did this:

if (isset($_GET['page']) && $_GET['page'] == 'my_plugin_page') {
   add_action('admin_print_scripts', 'my_admin_scripts');
   add_action('admin_print_styles', 'my_admin_styles');
}

If you didn’t, the the replacement send_to_editor() function will be on every page (including your add/edit post admin pages) and the media uploader won’t behave the way it normally does.

You can check to see if your ‘my_admin_scripts’ are being loaded by viewing the page source and looking to see if your script is in the head (my-script.js if you’re using the tutorial verbatum.)

Good luck.