Temporary HTTP 500 error after product upload

Hi,
I am getting a temporary HTTP 500 error after I upload any products. I checked the Apache log file and php log file and the php log file is showing: PHP Fatal error: Call to a member function getCondition() on null in .../.../public_html/vqmod/vqcache/vq2-catalog_controller_product_product.php on line 711

The HTTP 500 error stays there for approx 12-24 hours and then it goes away. Has anyone got any ideas?

Thanks

VQCache errors are originating from installed extensions. Not from the core. Uninstall the extension and see if the error 500 message persists.