Anyone have any idea how to solve this ?

so this happened more than once and on my different characters in different worlds , so sometime , we all talk to a npc to either start a quest or complete a quest , then there was once in perion , i was completing the quest , then i pressed the hot key 'n' to talk to the npc , then suddenly the screen froze and then pop me back to my desktop screen and maplestory will shut itself off , this happen more than once . The other time was in a different world , my luminous character was told to go to sleepywood to receive an augory ( crystal looking thing) , i talked to the npc and half way through his explanation , the screen froze and shut itself off again .

p/s i noticed that these situations happen in a pattern , normally I will talk to the npc and it will either gets shut off before or after talking to the npc . when i log back on these things will start happening over and over again :(

help me out , if i cant complete the luminous quest , im doomed :(