Ehm I think you didn't install properly.
This is what I did:
1. download MSSetupv111.exe
2. in the meantime I downloaded all the other WZ files aswell.
3. Installed MSSetup on my desktop in a folder, and named it BoredMS
4. Opend up all the WZ files(.rar's ) and extracted em into the same map where I got BoredMS installed
It asks then, overwrite? and you click yes for all.
5. Downloaded BoredMS client.exe
6. Opened maplestory with the Boredms.exe
And for 2 days now I can play without having problems
Hopefully this will help you out