You did not specify which version you are on. I am assuming it is NAV 2013 R2.
May I suggest that you try to the following steps:
1) Delete the user personalization for the id that you use to login.
Go to the user personilization page.
Locate the user that you use to login.
Click the Edit button.
In the new page click the Actions tab.
Click the Clear Personalized page button.
Log out and then log in and then try again.
2) Delete the object metadata of the page.
There are steps for deleting the object metadata objects and then recompiling the page object.
Do let us know the outcome.