I branched this off to its own discussion so that in case others are experiencing it they can find it more easily
We haven't been able to reproduce this in the lab since you reported it, so we're not quite sure what's going on. Our best guess is a different configuration or policy (AV even) than we're testing against.
Did the 6.0 installer work without any trouble on the same system? Do you have the same problem with the 6.0.1 installer on other systems?
Remote installer as Joel suggested might be a workaround, but I'm curious to see if others are running into this or if it's some kind of fluke, too.