The scan IP button in Jrunner has never worked for me even if it had glitched if I am getting the key through the LAN cable,I always got the timeout message no Xbox detected message. The only way I have ever got it to work is to go into my router DHCP section, where you will see whatever is conected on your network and if the console has glitched the Xbox will be listed as Xell with the IP address next to it. Then all you have to do is enter that IP in Jrunner and press get CPU key. Weird I know but I am not the only one that has happened to.
I highly recommend using the Nand X update cable with the QSB V3 though, it will work everytime if the console is glitching. Hope this helps.