Rooted phone, but can't pass "Install" dialog I am running Android 4.4.4 with the LiquidSmooth ROM and SuperSU. All these components work flawlessly, as far as I can tell. I am also able to use TitanicBackup (to demonstrate Root is working).

However, whenever I try to install an app that queries for special permissions (like Xposed from XPrivacy), the installer presents me with a "Cancel" and "Install" button at the lower end of the screen, but I can only tap "Cancel", but not "Install" (which seems to be disabled).

Any idea what's going on and how to fix this? I can workaround by manually defining permissions in SuperSU, but if I need to install a temporary download from the browser, for instance, the app/apk name doesn't show up in SuperSU, so i can't enable it to allow installation... :-/
This happens, when you have installed some kind of overlay app like Twilight. It is a security feature against screen manipulation.
Solution: Find that app and disable it. After that you will be able to hit the Install button.