I too am using x64 bit system and that means nothing, x64 systems run x32 software without any problem so the issue lies somewhere else.   It sounds like your download might have been corrupted or tempered with, for example if you have an antivirus it could be locking it up, however antiviruses only do that after you've already installed the game and they might only have a problem with LUNAClient.exe marking it as a false positive.   Have you tried re-downloading? Maybe using a download mana