My application has a paged scrollview. Each page of the scrollview has an instance of a view controller (buttonViewController) that shows a grid of buttons. If the user clicks on one of the buttons, buttonViewController launches a detailViewController modally, with animation set to YES.
If I'm viewing the first page (furthest left) or the scroll view, everything work's correctly. However, if I am scrolled to any of the other pages, the modal view animation (sliding up from the bottom in this case) doesn't appear. Instead, the whole view goes black for the same length of time that the animation would run for, and then the modal view controller appears fully displayed. The same thing happens when dismissing the modal view controller.
The code is completely standard. In my buttonViewController I call:
[self presentModalViewController:detailController animated:YES];
The same code runs no matter which page I'm looking at (though on different instances of buttonViewController of course.)
How would I start debugging this?