Well I have absolutely no idea what's causing this then. I couldn't find anything except a few people who are having the same error while trying to install random other applications - and nowhere can I find a general fix, except reinstall the application, which you already tried...
Do you have another PC in the house that you could install the game on? If so you can copy it over using the method I described here ->
Moving Aion over to my Laptop
Though on second thought, grrr that involves having the launcher installed already on PC 1...
If not...well it looks like something is not right somewhere in windows.