No matter what I try, I always get this error. I can't launch the game because of this error. I've tried deleting the files and putting the Launch exe in again and it worked once but when I turn it off and open it again I get the error.

Never heard anything like this if its not the updater then its your PC that's the fault, dunno really! try again delete:iw5m.dll,iw5m.dat and then copy the files again and update you IW5M and if this is not working then you have a serious problem!