When the user is on a certain page, there's no indication from the buttons in the navigation bar that this is the case. Each button looks like an equally valid "clickable" button. User testing has shown that this confuses people into thinking they should be able to click the button, and they become even more confused when that doesn't do anything.
SOLUTION
The buttons in the navigation bar should appear "disabled" when they lead to the current page.
PROBLEM
When the user is on a certain page, there's no indication from the buttons in the navigation bar that this is the case. Each button looks like an equally valid "clickable" button. User testing has shown that this confuses people into thinking they should be able to click the button, and they become even more confused when that doesn't do anything.
SOLUTION
The buttons in the navigation bar should appear "disabled" when they lead to the current page.