strange crash

Hello,
I have some tableViews and a navigationController behaving a bit instable and odd... For example:
If I select a cell in one of the tables this moves me further on in the navigation structure, ie to another tableview. Switching between those views with a "normal speed", works allright. BUT - if I click one backbutton and immediately select a cell in the tableview (ie I am to fast somehow) the app crashes with a bad exception...
I have viewcontrollers who are pushed when the user presses one of the table cells. The back button is a default/normal solution aswelll. Does anyone have advices on this?
I have looked for over-retaining but did not find anything. I also looked at the logic in the flow (viewDidLoad) in the tableviewcontrollers to see if something is called before it has been recreated (when back button is pressed)... but I did not find anything...

Does anyone have the same experiences here? Any advices? How do I have to reason in order to get this robust?
Thanks very much in advance!
MACloop