I have an effect in Windows 8.1 that I'm sure wasn't there when I installed Windows and seems to have appeared in the last 2 or 3 weeks.
Basically I can't click on a Window in the background and bring it to the front. It's as though the current top window won't stop being top. I have no utilities that would support such a function as far as I know. Sometime it seems to work fine after powerup and then starts misbehaving after a few applications are running.

The workaround seems to vary too - sometimes I can right-click on the task in the taskbar then select the application name and it comes to the front, sometimes I have to press Alt-Tab once then I can select the background window. Sometimes I have to minimise the top window. Sometimes I even have to exit the 'top' program. Sometimes I tear my hair out, this is such a fundamental windows feature since Windows 1 & in all other window systems I just can't believe it's a Windows 8.1 feature....
With Alt-Tab I can switch between windows but the selected application still stays behind the current top window.
Despite googling I can't find any mention of this phenomena, although there are several utilities that allow you to keep a window 'on top'.

It's a self-made PC, originally with Win7 but with Windows 8.1 installed clean on a new SSD . I have dual monitors though I have the second monitor switched to a laptop during the day, with Windows 8.1 set to display on the primary monitor only. With Windows 8.1 on both monitors it is slightly better because I can move windows to the other screen.

Does anyone know what might be wrong and how I can fix it?