My problem is similar, but not the same:
Content element: K2 Items.
overwrite the values - apparently at least - in the Translation / K2_Extra_Fields, then I apply or save them, it's the same - there is no change at all. I can't translate the values of the Extra Fields in the K2 Items . Any other ones are OK, I could translate the Extra Fields, the Categories, and in the Items: title.
"Copy" is inactive, but I'm afraid: not this is the real problem.
Site: Medical staff
(Dept Surgery, Univ Szeged/Hungary)
Joomla 1.5.22 Stable
JoomFish 2.1.7 (upgraded recently, after my first trial and the problem above)
K2 2.3 (upgraded recently, after my first trial and the problem above)