UITabBar Application crashes in iOS 5

[Starhopper108]

I have a tab bar application with 4 tabs, each tab being a navigation controller housing a view controller with a table view. The application worked fine in iOS 4 and earlier, but now that I try to run it on iOS 5, i'm getting 'EXC_BAD_ACCESS" on this line in the stack:

0x0040a8c1  <+0012>  call   0x40a8c6 <-[UIView(Hierarchy) _makeSubtreePerformSelector:withObject:withObject:copySublayers:]+17>

and also at:

[window addSubview:tabBarController.view];

in my app delegate's implementation file. I've looked up some changes that have been made in the conversion from iOS 4 to 5, like changing the code in main.m, but to no avail. Any help would be appreciated