Can't pickup a quest item

Describe the problem. Be as specific as possible!: When I made a Cygnus Knight and accepted the quest where I have to get a cynical mushroom doll, it says that the game files have been damaged and that I have to reinstall the game. At first I thought some of my files might have been messed up because I didn't have MapleStory patched properly on this computer or something, so I uninstalled it and used the start button on the website to reinstall it. The problem wasn't fixed.

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