Order email advice second order showing zero follows actual order

[shags38]

when an order email advice comes through a second order showing zero and no customer details follows - the second order is consecutive to the first order (i.e. order #370 followed by 371) and has the same transaction i.d. number - has only been happening for about a week now - any ideas on how to correct this?

site www.harmonyballpendant.com

[mc12345678]

when an order email advice comes through a second order showing zero and no customer details follows - the second order is consecutive to the first order (i.e. order #370 followed by 371) and has the same transaction i.d. number - has only been happening for about a week now - any ideas on how to correct this?

site www.harmonyballpendant.com

Been seeing this reported more and more recently.

Plugins installed? Method of payment? Additional files in the observers directories?

Error logs in the logs directory?

[shags38]

Been seeing this reported more and more recently.

Plugins installed? Method of payment? Additional files in the observers directories?

Error logs in the logs directory?

Using PayPal express
error logs as follows;

[15-Apr-2015 09:28:55 Australia/Melbourne] PHP Warning: Creating default object from empty value in /home/zzzzz/public_html/includes/modules/shipping_estimator.php on line 117

[15-Apr-2015 09:29:36 Australia/Melbourne] PHP Warning: Creating default object from empty value in /home/zzzzz/public_html/includes/modules/shipping_estimator.php on line 92

[15-Apr-2015 09:30:11 Australia/Melbourne] PHP Warning: Creating default object from empty value in /home/zzzzz/public_html/includes/modules/shipping_estimator.php on line 107

[15-Apr-2015 09:35:39 Australia/Melbourne] ERROR: Failed sending email to: " " <> with subject: "Order Confirmation No: 371" (failed validation) .... this is the order with no details

[15-Apr-2015 09:35:39 Australia/Melbourne] PHP Warning: Creating default object from empty value in /home/zzzzz/public_html/ipn_main_handler.php on line 354

Additional files in the observers directories? not sure what 'observer directories' are

plugins; none that involve any of these files/functions

[mc12345678]

PHP version? (Admin panel, version option)

[shags38]

PHP version? (Admin panel, version option)

PHP Version: 5.5.22 (Zend: 2.5.0)

[mc12345678]

PHP Version: 5.5.22 (Zend: 2.5.0)

ZC 1.5.1 is not compatible with PHP 5.5

• Zen Cart v1.5.1 is compatible with PHP 5.2.14 thru PHP 5.3.x. Requires some patches to work with PHP 5.4, and upgrading is a better idea.
  
  (* NOTE: v1.5.2, v1.5.3 may technically work with as low as 5.2.14 but will be less secure, so should use PHP 5.3.7 or greater.)
  
  
• Zen Cart v1.5.2 is compatible with PHP 5.3.7* thru PHP 5.6
• Zen Cart v1.5.3 is compatible with PHP 5.3.7* thru PHP 5.6
• Zen Cart v1.5.4 is compatible with PHP 5.3.7* thru PHP 5.6 (recommend PHP 5.4 or 5.5)