VQmod related error

I'm using OpenCart 1.5.4.1 with VQmod 2.2.1 and Mod Manager 1.0.1. All was fine until HostGator's reseller servers took a three day nosedive. The site itself is working, orders are placed, shipping is selected and emails are going out. People have started mentioning some SQL errors however that I'm trying to find. The one helpful email told me that when she clicks the link in her order email to see the order she placed, she gets this:

Notice: Undefined index: HTTP_REFERER in /home/dep22/public_html/vqmod/vqcache/vq2-catalog_controller_account_login.php on line 66Warning: Cannot modify header information - headers already sent by (output started at /home/dep22/public_html/index.php:104) in /home/dep22/public_html/vqmod/vqcache/vq2-system_engine_controller.php on line 28Warning: Cannot modify header information - headers already sent by (output started at /home/dep22/public_html/index.php:104) in /home/dep22/public_html/vqmod/vqcache/vq2-system_engine_controller.php on line 29

The Mod Manager error log is empty. So I'm not really sure how to proceed in tracking this down. Any ideas?

Thanks!

HG might have modified something here? Anyways, were you able to find out on what caused this issue? Similar issue below.

http://forum.opencart.com/viewtopic.php?f=131&t=125337

I have no idea. I never found a solution but no one else has complained and I don't get the error myself.