IPhone : UITabbarController Inside UINavigationController

I am using a UITabBarController inside a UINavigationController.Inside The UITabBarController there is 2 UITableViewController , the first table view (which is selected by default )shows correctly while the other tableview are partially hidden behind the navigation bar , when adding

self.tableView.contentInset = UIEdgeInsetsMake(64.0f, 0.0, 0.0, 0.0);

this fix the problem but the weird thing when adding action to present a new view controller modally using

    [self presentViewController:viewcontroller animated:YES  completion:nil]

and then the user dismiss this view controller using

[self dismissViewControllerAnimated:YES completion:nil];

the second TableView is shifted down by 64 + 64 ,,, how to fix that to keep the second tableView shifted by only 64