I downloaded them myself, and when I opened my Maple Story folder, my NOD32 detected them as Trojans and removed them. Its called Win 32/PSW.Mapler.AJ Trojan.

They seem relatively harmless.... Is it an oversensitivity on NOD32's part?

Hello would you please submit that file to Jotti's malware scan and /or Virustotal and post back their reply to you here,thanks.

Also tell your operating system.

File: KDMaplestoryClient[GMS]0.54.exe
Status:
INFECTED/MALWARE (Note: this file has been scanned before. Therefore, this file's scan results will not be stored in the database)
MD5: 1a547bf6661cfcce424705b045a462bd
Packers detected:
-

A-Squared
Found nothing
AntiVir
Found nothing
ArcaVir
Found Trojan.Psw.Mapler.Aj
Avast
Found nothing
AVG Antivirus
Found PSW.Generic6.MNT
BitDefender
Found nothing
ClamAV
Found Trojan.Spy-38010
CPsecure
Found Troj.PSW.W32.Delf.oc
Dr.Web
Found nothing
F-Prot Antivirus
Found nothing
F-Secure Anti-Virus
Found nothing
Fortinet
Found nothing
Ikarus
Found Trojan-PWS.Win32.Mapler.aj
Kaspersky Anti-Virus
Found nothing
NOD32
Found Win32/PSW.Mapler.AJ
Norman Virus Control
Found W32/Mapler.BD
Panda Antivirus
Found nothing
Sophos Antivirus
Found nothing
VirusBuster
Found nothing
VBA32
Found Trojan-PSW.Win32.Mapler.aj

Upon further reading this appears to be a false positive.
Disable your anti virus for this and only this download, Do Not go anywhere else.
Go to this site and dowload the latest patches( I think it is v54 & 55) from here http://maplecrusade.com/
Put them in the Nexon MS folder.
Going into the AV program,find the exceptions section.
Click the exceptions button (or what ever it takes to enter)
Designate Nexon Folder as an exception.
Click OK or apply to accept the folder as Excused from the scanning process.
Re-enable the AV program.