His problem is that he has a corrupted mappack. Deleting Mari0 will not fix this. Deleting the settings will allow him to get back into the game, but it will still crash on that mappack. He needs to delete that mappack.
If you're still reading this topic, click start, then Run. Type %appdata%. LOVE -> Mari0. Then, you can delete the mappacks folder, which will fix your problem, but it will also delete all your mappacks. You can also go into the mappack folder and delete the corrupt mappack. You have to delete the whole folder, not just the files inside the folder.