If ViewController is the root view controller, it can’t present a modal view controller from within its own viewDidLoad, because at that point it doesn’t have information like the screen size.
If other view controllers have already displayed, this will work. If the root view controller is a UINavigationController, you will see a view sliding in from the right while the modal view slides up from the bottom.
Anyway, for your ViewController, the soonest you could present it is after it has become visible. Using a timer for this is unreliable; older and slower devices have dramatically longer load times.
For more reliability, implement viewDidAppear: for ViewController. Do still use your timer system to add an additional delay; a fraction of a second should be sufficient. Although presenting the modal view controller from within viewDidAppear worked for me in the iOS 5.1 simulator, Presenting a modal view controller when loading another ViewController says it sometimes doesn’t happen.