I upgraded to ics via kies a while back, and have two things to say:
-I don't remember for sure, but i am 95%certain you cannot upgrade to ics over Kies air. You need to physically connect your phone to the computer with a usb and use regular Kies.
-Don't upgrade to stock ICS. It is terrible, and imo NOT an improvement over stock GB. I had never felt the need to root my phone until i unknowingly installed stock ICS. Within two days i had enough and wanted it off my phone, even without knowing about the emmc bug. If you really, really want ics, I'd suggest skipping the upgrade altogether, root your phone while you are still on GB, and then flash any of the custom ICS ROMs in this forum.
AT&T Samsung Galaxy S II (I777)