Universal app working on iPad 1 but not on iPad 2

First of all I want to say that I'm I aware that my question is probably way too vague to answer and may be closed/down-voted. I just hope for some inspiring brain-storming on possible solutions.

Here's the story:

My app was crashing on iPad 2, but not on iPad 1. I've fixed the crash related to unarchiving nib and now I have a very strange problem - my universal app still runs without any problems on 1st gen iPad with iOS 4.2.1 and 4.3.3, but not on (some/all?) iPads 2 with 4.3.3. Unfortunately I don't have an access to iPad 2 with iOS < 4.3.3 to test further and narrow down the problem.

My app has it's main screen displayed by using presentModalViewController. My modal VC is MGSplitViewController (it mimics native UISplitViewController and enhances its functionality). When my VC is presented, only "root view" is displayed and remaining part of screen for "detail view" is just black and empty however the controller is loaded and active (debug logs are printed etc.).

So on iPad 2 I have access to, it fails to display detail view properly, however I've heard from one user that it's fine on his iPad 2 (both iOS 4.3.3). App also works ok on iPhone/iPod regardless iOS version, so I assume it's related only to iPad code of my universal app.

I believe it may be more general issue with displaying views. I've tried to read view property of my detail view, which should force view to be displayed, but it didn't help. It may also be related to IB stuff (the initial nib unarchiving crash only on iPad 2??), but I think everything is wired ok in IB...

Anyone has a slightest idea how to investigate this problem?

EDIT: BTW: My iPad 2 is giving m开发者_如何学JAVAe hard time as it drops Wi-Fi connection very often. Other people are also reporting this kind of "feature". Can it be that it's just something wrong with my iPad 2?

EDIT2: the app is also not correctly displayed on iOS 3.2, 4.2 and 4.3.3 Simulator (via XCode 4), but gets displayed correctly on iOS 3.2, 4.2 Simulator via Xcode 3. Strange, isn't it?

Anyone has a slightest idea how to investigate this problem?

If you'll allow a somewhat vague answer to a somewhat vague question, then yes, I do have an idea.

To approach problems like this in general, bisection of the problem field is a great way to go forward:

• You identify the general problem area. Could it be presentModalViewController in your case?
• Then about halfway through the code in question, you set a breakpoint/write a message to a log file/play a sound/send a mail/tweet/whatever it takes to verify that your code has come that far without a crash.
• Run it and see if your message has been produced.
• If it has been produced, the problem is not in the first half, so it must be in the second half (a log message at the end of the identified problem area is useful, too, just to make sure that the crash actually happens before that).
• On the other hand, if there is no trace of your log message, then the crash must occur in the first half, and you can rule out the second half of your code for this particular problem.

Now you repeat the algorithm by setting your breakpoint/log message about halfway into the culprit half you just identified.

Repeat until you find the problem. It won't take many iterations.

Of course, the crash may be due to some variable stored at a previous step or in another method, but now you know where to look.

Initially the app was crashing due to unarchiving the nib. I don't recall the exact crash output, but it was quite strange for me that same nib was properly unarchived on iPad 1 with same OS version, so I suspected that the problem lies in xib file... I've recreated the xib from scratch routing everything carefully and - bam! - it started working on both iPad 1 and iPad 2! How come some nibs aren't unarchived in a same way on same OS running different HW???