download the new client i made, my antivirus had the same problem with the old one but this new one has no problems (for me it doesn't anyway) plus it has super tubi and UFJ
http://kxk.me/?TwistedstoryV75
and no, his/her antivirus isn't being stupid, it's being clever, some maplestory base clients have this trojen.gen.2, harmful and non-harmful versions to be able to operate, especially the earlier clients as its a hacked client, mine is clean (and custom) from the old TwistedStory server
if you ever get a trojan flag from a client, make your own, find out the server IP and hex it into a fresh, clean client