[MarketPress + WPML] Some strings are translated but displayed in english

Hi, I've an e-commerce site based on market press and wpml and I translated manually every string by WPML > String translation menu.
Testing the site I noticed that some strings (in checkout area) are displayed in english when i surf the site in italian or in french, so i checked those strings by searching them in string translation, and they result translated -i checked that the translations are really in the right language, and they are, but i always see those strings in english.

I posted this same topic in WPML's forum (here: http://forum.wpml.org/topic.php?id=4297#post-19864) and the result seems to be that those strings are hard-coded in marketpress. Is it true? What should I do?