Invisible Modal Windows

I installed Windows 10 in a VM (Hyper-V) to see if it was good enough to be installed on my real computers. The first thing I needed to do is activate it. I remoted into the computer, went to the activation screen, and clicked the "Change License Key" button. Nothing seemed to happen, so I tried clicking it again. This time I got a "ding" sound. I tried clicking on some other things and kept getting that sound. It seemed like there was a modal dialog open that I couldn't see. I pressed Alt-F4 and everything returned to normal. None of the windows I could see closed but I could click on everything again.

I clicked on the button again to see if I could find the window. The settings window became unclickable again, there was nothing in the taskbar, alt-tab didn't show any new windows. Alt-F4 returned it to normal. Out of curiosity I tried it from Hyper-V. Same behavior. I would post a screenshot, but, you know.

Invisible modal windows. How could they make something so broken? The mind boggles. I wonder how many others there are. Of course the workaround is to use the command
     slmgr.vbs -ipk xxxx-xxxx-xxxx-xxxxfrom an elevated command prompt. I was really looking forward to upgrading to windows 10 but it's clearly not ready if you can't see some windows through remote connections. Guess I'll be waiting for whatever form service pack 1 takes in this new system. That's why I hate Microsoft today.