App works on device via direct install but doesn't via ipa

Question

I've been surfing the net and have found no answer to this situation I have (though I find it surprising because I can't believe I'm the first one to come over this). Maybe I don't know the correct keywords for finding it...

My problem is I build an iOS app with XCode 4.2 and test it running directly in an iPhone 3G with iOS 4.2.1 and everything runs as it is supposed to. However, if I build an .ipa and install it in that same device (where I have previously uninstalled the former installation of the app), it install perfectly and almost all the app works fine... but for one place that is not working properly.

I don't enter in details of what is exactly happening because it is something that has happened before in other apps with other devices (i.e. ipad 1, iphone 4...) (once I found out that compilation and execution directly to a Device was letting an uninitialized rect being added to something, while in .ipa it crashed (I think it was a SIG_ABRT but don't know exactly).

Is this situation documented anywhere? What cases compile in one way and others don't?

Thanks in advance!