I think this is a new bug in the latest version of the iphone app - not noticed it before
I have in-line subtasks in context view. If i Scroll to the bottom of the subtask in Task Details, usually where it says Parent (I think as it crashes I can't recall what the actual button says), it crashes the app.
This does not occur when viewing the parent task with Nested view where I can scroll to the bottom of the Task Details and it will say X Subtasks. It also lets me scroll to the bottom of those tasks, so the bug must be at the point where it determines what a tasks parent is.
We have already fixed this bug and submitted it to Apple for approval. I don't know how long it will take Apple to approve it.
In the meantime, if you go into the "fields & defaults" settings page and disable some fields that you use less frequently, it will alleviate the crashing. The problem only happens when the "Parent" row is off the bottom of the screen.