Hm. We can see that right away CubeCart is told to use fr-FR, but the phrases are not coming from that language pack. (See Debug Messages[0])
Please examine the following and try the suggested action:
In admin, Languages, take note of any actual entries in the Domain column (not the slightly greyed-out suggested examples).
If there are actual entries, blank them out and Save.
Have CubeCart clear its internal cache.
Did anything change?