I am working on a project to upgrade CRM 4 to CRM 15. I did that on our test environment for now. Everything is working fine Except the navigation links on the horizontal navigation bar for our main entity (contact) is not working. When I click on a navigation link for a contact record it does not display anything and stays on contact form. The navigation bar is working fine for all other entities, they are not just working for contact. I checked the mappings for contact with other entities and they are correct.
Can anyone help me with this?
I'd try the following (very quick to try, and it can't do any harm):
Go to the Contacts form view (under customizations).
Click in the left hand navigation pane and then remove the links to the related entities (as you would remove a field). Save and publish all your changes.
Go back into the form and re-add the navigation pane items that should be displayed. Save and publish all your changes.
That could reset whatever setting has got screwed up.