There are few reasons i can think of: (i have this problem in another PC too)
-u don't have the wz files u need to start the game.
new wz files download:mediafire.com 8pomy248gjz6y8l
optional wz files download:megaupload.com CXE6021Y
v62. download:http://megaupload.com/?d=1Hfcwfpq
-your antivirus is blocking IdyllicStory,unblock the files of the game or turn off your antivirus.
-u tried to login when the server was off. (im not sure about that reason but it can be why the game dosent work)
-Restart your PC
-u didn't replace all of the files so the game cant work
-Re-download the game files and replace them.
Hoped i helped,Priseless.
P.S:the links i gave u will transfer u to google,you will get a result of the topic with the good links