Your antivirus (Norton, AVG, MacAfee) probably thought it was a virus. add it to your exception list.
Posted via Mobile Device
I can remember antivirus applications found a Themida virus. Known problem :|. Even unpacked btw. You could try to remove the now unused Themida code section at the end of the file.
STREDIT (Old MS | EMS)| GetKey DLL | NX Mirror | MapleShark | TinyMapleServer | IDC script | AutoPatcher
Previous localhosts that I've inspected are packed with Themida, which causes the false positive. Be aware that it's not recommended to host your localhost on your webhost, as it will be flagged as a false positive and you will be accused of distributing malware.
Oh, and another thing, MapleStory fixed this by digitally signing the executable afaik :P
STREDIT (Old MS | EMS)| GetKey DLL | NX Mirror | MapleShark | TinyMapleServer | IDC script | AutoPatcher