Customer remains on Review Order page after placing order

When the customer hits the "Place your order" button on the "Please review and submit your order" page, the order is submitted but the user is left on the same page with no feedback that the order has been processed.

Payment module enabled: cod

This happens on both live and test servers:

Live:
Red Hat ES3, Apache 2.0.46, MySQL 4.1.20, PHP 5.0.4
Drupal 4.7.4
ecommerce - 4.7.x-something (newest file cart.module,v 1.133.2.14 2006/11/29)

Test:
Mac OS 10.4.9, Apache 1.3.33, MySQL 4.1.21, PHP 5.1.4
Drupal 4.7.4
ecommerce 4.7.x-3.0 (newest file flexicharge.module,v 1.8.2.1.2.8 2007/03/10)

Dave