Error Log Report Please Help

[11-May-2012 12:33:57 UTC] PHP Fatal error: Class 'Controllercommonheader' not found in /home/rasa/public_html/vqmod/vqcache/vq2-system_engine_controller.php on line 43
[11-May-2012 16:36:25 UTC] PHP Fatal error: Class 'Language' not found in /home/rasa/public_html/index.php on line 186
[11-May-2012 19:15:36 UTC] PHP Fatal error: Class 'Registry' not found in /home/rasa/public_html/index.php on line 31
[11-May-2012 19:26:02 UTC] PHP Notice: Undefined index: HTTP_HOST in /home/rasa/public_html/index.php on line 49

Im getting these errors very frequently. I can't reproduce these errors. Not sure if they are related and its driving me nuts.
I know some of my customers have had trouble checking out.

Please Help. Thank You!

You are missing some files. That is the short answer...but accurate. Make sure that you have all files in place. What version of OC are you using and what version of vqMod?

I'm using opencart 1.5.1.3 and vqmod version 0.2.
my url is rasahydroponics.com.

where should i be looking to find the missing files?

Bump. I need this fixed. I'm willing to pay.

And this error yesterday

Class 'Controller' not found in /home/rasa/public_html/vqmod/vqcache/vq2-catalog_controller_common_maintenance.php on line 2