I attempted the same at a Kmart a few weeks ago. The system drained my Sears GC, but they could not get the GC I was trying to buy to activate, and they tried a couple of different GC. And they couldn't get the system to refund the value back to my Sears GC. So I walked out with a crisp 50 dollar bill for a refund, I'll take that any day. I guess the activation network was offline or something.