I'm using Windows 8, when I try to use the magnifying glass tool any of the viewmodes work, the docked mode is gray, and the lens mode is a white rectangle, I can't magnify.
Also I have the same problem when trying to use the "Live Zoom" viewmode of "ZoomIt" application from "SysInternals", it turns full Gray.
EDIT: But i've tested other applications and can magnify well.
I've readed the supposed solution here: Windows 7 magnifier not fullscreen But that solutions are not for Windows 8, I've followed the steps but doesn't repair nothing.
Trying to repair this I ran all services, also of course I have Aero enabled (It's Windows 8...), and also the themes services running, the magnifying window stills gray.