Error Page when updating products

This is what I get after I try to update a product
This is not constantly the same - sometimes happens, sometimes does not

"Notice: Undefined index: option_value_id in /home/content/44/6571744/html/mystorefolder/admin/model/catalog/product.php on line 169Warning: Cannot modify header information - headers already sent by (output started at /home/content/44/6571744/html/mystorefolder/admin/index.php:83) in /home/content/44/6571744/html/mystorefolder/vqmod/vqcache/vq-system_engine_controller.php on line 28Warning: Cannot modify header information - headers already sent by (output started at /home/content/44/6571744/html/mystorefolder/admin/index.php:83) in /home/content/44/6571744/html/mystorefolder/vqmod/vqcache/vq-system_engine_controller.php on line 29"

Annoying as I cannot really tell when would I get the error.

Any ideas?

"Cannot modify header information - headers already sent" means, in most cases, that you have spaces after the ?> in your language related files.