Unable to create a MapleStory.exe new file

I was having a similar problem to this. My antivirus (NOD32) was picking up maplestory.exe as a virus. We didn't figure this out till I had a friend try to send me his maplestory.exe and NOD32 picked up that one as a trojan and quarantined it. I imagine this was happening everytime I tried to patch. (I tried several times because I happened to have the last install)

I disabled NOD32 and everything worked fine. NOD32 updated later that day though and I haven't had the need to disable it since i finally patched properly.