well of all these posts i didnt see a correct answer.. the NGMdll.dll file that it gave you the error for is your problem.. you probably just lagged at an inopportune moment and the files downloaded sections got mixed up.. you need to go to the path where the file is and delete it.. then try downloading again...
also.. the file path given in the error report for NGMdll.dll is the path that it downloads the install to before executing it.. your temp folder.. same for everyone else, but the path is different.