I had the same problem....however it was easily fixed by uninstall and re install of kies...however once the firmware downloads kies goes into a dim black state of idle time....if i click on it it says not responding...i read this on one of the sites, Note: The time to upgrade your device will vary. Dependent upon your computer and network connection, you may experience some idle time or slow response in Kies. Do not close any programs on your PC, disconnect or turn off your device until the upgrade process is complete.
not sure how long this stupid thing is to idle....its been like this for an hour WTF....any solutions...stuck