iTunes doesn't see my iPhone in DFU mode

I'm trying to downgrade from 7.1 beta 2 to 7.0.4. I put the phone in DFU mode (screen is black), and open iTunes. Nothing is recognized. I take it out of DFU mode, and iTunes sees it fine. Why am I not getting a pop-up in iTunes that I need to restore it while I'm in DFU mode? Never had a problem before.

(On iPhone 5, Windows 7, with latest iTunes.)

 

The only solution I could find was to try a different computer, which solved my problem.