My Blackberry won't show unread texts, has anyone had the same problem? How do i fix it?

no i havent had that problem but its a case of remembering when it was working ok and the last thing you did before the problem started. as you installed the new app you could try a hard re-boot (remove battery with phone still on and then replace) it can reset the phone for you. if that fails then you may need to consider removing the app and see if that cures the problem.