I had the same problem earlier, and had tried doing the things a few of you have stated. However i found the fix for me to be for this problem:
1. Right click Aries.exe and create a shortcut, right click that shortcut and select Properties.
2. Go to Shortcut.
2a. Look in target to see the lines C:\Nexon\MapleStory\Aries.exe
3. Change lines according to this C:\Nexon\MapleStory\Aries.exe GameLaunching
4. Apply settings and run shortcut as Administrator.