Strange. Ouendan 2 never complained about wrong save type, it evaporates saves whenever type mismatches.
Actually I'm curious how games have "can't save" messages, when most people (people who bought the game) won't be able to make the game save with wrong save type anyway.
So far I've experienced save evaporate with Pokemon Diamond and OTO2. Don't think any other games had problems. Pokemon save evaporated once, I updated her firmware to 1.23 and since then no problem. And OTO2, in an hour or so after save evaporates, she can beat everything and go back to playing Cheer Girls on hidden.
She screwed up nothing besides choosing a wrong save type after saving properly with correct save type. I know this because I lost her save once because I didn't notice the save type was changed back to unknown after putting in a new game. And when I changed it back to correct type and re-ran the game the save was gone. Before that it saved properly because I did it myself and checked 4 times to confirm it saves and doesn't disappear.
Anyway, I'm updating hers to DS Linker 1.39 firmware hopefully save evaporates less frequently