The latest development snapshot of entity_translation module (which is soon to be released as beta version) requires two parameters while calling the function entity_translation_tab_access(). The first parameter is entity type and the second one is the entity.
Currently commerce_product module only has the first parameter which works with previous version of entity_translation. Now because of the missing parameter in the function call, this throws a warning and subsequently a fatal error which is why I have marked this issue critical.
Following is the error that I received when navigating to
Warning: Missing argument 2 for entity_translation_tab_access(), called in sites/all/modules/contrib/commerce/modules/product/commerce_product.module on line 890 and defined in entity_translation_tab_access() (line 678 of /sites/all/modules/contrib/entity_translation/entity_translation.module). EntityMalformedException: Missing bundle property on entity of type commerce_product. in entity_extract_ids() (line 7562 of /includes/common.inc).
The solution is very simple however. The function call entity_translation_tab_access() just needs to be called with the second parameter by passing the product entity.
Patch follows. Patch is simple and straight forward. Without this, entire product adminstration is not unusable.