[edit] The game seems to not find the right savegame directory. Even when there are are valid files in /Data-1.13/SavedGames the game shows no saved games ('continue saved game' is greyed out)... the game probably tries to access some directory, it doesn't have writing rights for, while saving (just my guess)
[edit2] My failure... it doesn't even use /ja2-1.13/Data-1.13/SavedGames but /ja2-1.13/SavedGames, so this couldn't have been the problem.
The only thing I understood of the savegame code is, that there are a whole lotta possibilities that could lead to an error... ugh...