A simple uninstall from the control panel can leave a lot of stray registry entries, etc, behind. That's why I used Revo, because it scans for leftovers and everything can be deleted. Something like CCleaner, run after an uninstall from the control panel, might work too, but I'm just guessing. (CCleaner is free.) Like DVM, I got the same error when uninstalling, but the uninstaller still found the registry entries and I deleted everything it displayed. I'm running Windows 7 64 bit.
Have just seen dlu's post after having this error and already doing what he suggested. I've used Revo for ages and it worked for me but no doubt there are others that would work equally well. Did a complete uninstall then downloaded 4.6.4 and it installed fine. I did have to clear IE's cache before I could sign in to the fresh install, but all seems to be working fine now.