confusing bug regarding IBOutlets-Collection of common programming errors

Iv been breaking my head on this for long but im just not able to figure it out.

In the view Did Load method of my view controller if i try to make some changes to an imageView connected by an IBOutlet, it is non-responsive. It simply does not respond to any changes im making to IBOutlet elements. For eg: if i have an imageView in IB and its connected thru an IBOutlet and i try to set the hidden property of this ImageView it does not respond. Why this is so is beyond me.

I then added that imageView to another view and added the combination as a subView to this view. Then I could make changes to this imageView elements. But if i try to access this imageView in another method other than viewDidLoad, the application crashes. The imageView is an instance variable.