TabBarController not working with different nib files

Question

Hi, I've got a tabbarcontroller, and a MainView.nib that houses 3 Views and ViewControllers within the MainView.nib.

When I try to associate another nib with its own ViewController to the fourth tabBar, I get errors on tapping the bar,

I'm probably doing something wrong cuz usually the same principle works perfect in a non tabBarController.

I wasnt able to find a good video tutorial for this...

any light on this is very appreciated..