I have this problem with my n900, i can't type in the upper app, im using swiftkey keyboard. This happened to me after upgrading to kitkat.
I tried undocking swiftkey and ir worked also used stock samsung keyboard and also worked, can this be a big from swiftkey with the kitkat?
Another issue is when i try to edit the multiwindow apps the optiom to go to the playstore doesn't exist.
Hope from some help, thanks.
Sent from my SM-N900 using xda app-developers app