In addition to what BluesBear wrote, when you say that nothing is attached to the board running Blink, I'm guessing the USB cable is attached, otherwise you couldn't run it. So I suppose you mean that nothing is attached that allows the two boards to communicate between each other, since you also mentioned things like bluetooth? Anyhow check in system->hardware in control panel and make sure there aren't any exclamation marks anywhere around the COM port or USB hardware entries. I'm also confused as to why you run two separate versions of the IDE when just two instances of the IDE, same version, with each arduino/IDE making use of it's own COM port would "seemingly" accomplish the same thing, better?