CiviEvent Listing module in Joomla not finding database table
Sounds like you also need to update the settings inside your file that points to your Joomla database. I don't know exactly where that is, as I use Drupal. But mine is at /home/username/public_html/sites/default/settings.php. That is where I tell Drupal how to connect to its database. Every CMS I've ever worked with has something similar. Inside that file is a listing of CiviCRM database tables so that your CMS can connect. If you haven't changed it there, then Joomla is still looking for the old database.

Edit:

The lines you're editing in your CMS's settings file would look similar to this below. Unfortunately it doesn't get formatted right when pasting in here, so I've only included the first dozen lines or so.

$databases['default']['default']['prefix']= array(
  'default' =&gt; '',
  'civicrm_acl'                              =&gt; '`username_civicrm`.',
  'civicrm_acl_cache'                        =&gt; '`username_civicrm`.',
  'civicrm_acl_contact_cache'                =&gt; '`username_civicrm`.',
  'civicrm_acl_entity_role'                  =&gt; '`username_civicrm`.',
  'civicrm_action_log'                       =&gt; '`username_civicrm`.',
  'civicrm_action_mapping'                   =&gt; '`username_civicrm`.',
  'civicrm_action_schedule'                  =&gt; '`username_civicrm`.',
  'civicrm_activity'                         =&gt; '`username_civicrm`.',
  'civicrm_activity_contact'                 =&gt; '`username_civicrm`.',
  'civicrm_address'                          =&gt; '`username_civicrm`.',
  'civicrm_address_format'                   =&gt; '`username_civicrm`.',