can't install backed up apk

I'm having a problem with re installing backed up apk's - I get to the android screen saying 'do you want to install this application' at the bottom of the screen there is two buttons - the right says 'cancel' and the left says 'install' when I click on the install button it just wont press like it is frozen, although the cancel button works fine. I'm sure this is probably a really simple setting problem but I can't for the life of me work it out, can anyone help with this please?

 

I used 'clickfree' and also 'app backup and restore' I think the problem is broader than this though as I tried to install swiftkey flow beta the other night and got the same screen (which I think is an indigenous android menu) which wouldn't let me click the install button, this has also happened when I have tried to download icon sets. I have allowed installation from unknown sources in the global settings.

I'm stuck, your help is much appreciated.

Jim

 

I finally have worked out the problem - I have 'screen filter' installed, when I have the shade on the install button won't work, solution is to turn the screen shade off and screen brightness on full. Conclusion = must be a bug with screen filter.