In landscape mode there are 4 rows of 5 icons
In portrait mode there are 5 rows of 4 icons.
Roughly where is the strip?
Does it happen on just one screen?
my thoughts are that either the screen is faulty or you have apps that are not compatible with your version of iOS so they don't do anything when you try to run them.
Lets say the app is called CHRISSA and in landscape mode it doesn't work. Now turn the ipad through 90 degrees - the app will have moved position - try it and see if it opens. If it opens, the try the app that is now in the spot where CHRISSA was in landscap mode. eg in landscap it was 3 across, 4 down, in portrait try the app at 1 across, 3 down. If that doesn't open in portriat mode but does in landscap then could be a faulty screen.