Is anything else besides the game blurry? It could be that your display and/or graphics settings were/have changed somehow.

Hm weird. Only thing I could suggest would be clearing the game's cache. And by that I mean going to your users/[username]/appdata/roaming folder and finding the "naruto online" folder and at the least putting it in the recycle bin, then relaunch the game. Fair warning this will cause you to have to relogin completely and it will have to redownload the game files it cached before.