为什么我的UIView在重新加载后没有响应?

我有一个viewController,可以弹出一个带有UIWebView的模式视图。如果我访问一个特别重的页面,我会收到内存警告,然后父视图会被卸载。这一切都很好,但当我关闭模态视图时,我的父级会重新加载(如预期的那样),但不再能够处理任何触摸事件。应用程序对方向的改变做出正确的反应,但再多的触摸也不会改变任何东西。按钮不起作用,UIWebView不响应滚动(但加载默认网站),等等。就好像有一个透明的UIView覆盖了我的整个窗口。你知道为什么会这样吗?

BrowsingViewController* controller = [[BrowsingViewController alloc] 
    initWithNibName:UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad ?     
    @"BrowsingViewController-iPad" : @"BrowsingViewController" 
      bundle:nil initialURL:[[request URL] absoluteString]];    
[self presentModalViewController:controller animated:YES];      
[controller release];

下面是我如何(从模态视图本身)消除它的:

- (void) onCloseTouch
{   
    [self.parentViewController dismissModalViewControllerAnimated:YES]; 
}

在浏览视图层次结构时,我没有注意到任何异常。下面是我的主视图控制器的日志语句。它们在我显示模态视图之前和之后都是相同的:

viewWillAppear called.
=============== parentViewController subviews count=2
View [0] is a UINavigationTransitionView
subview count=0
View [1] is a UINavigationBar
subview count=2
      subview [0] is a UINavigationItemView
      subview [1] is a UINavigationButton
=============== self views subviews count=3
View [0] is a UIWebView with tag [1]
subview count=1
      subview [0] is a UIScrollView with tag [0]
View [1] is a UIToolbar with tag [2]
subview count=3
      subview [0] is a UIToolbarTextButton with tag [0]
      subview [1] is a UIToolbarButton with tag [0]
      subview [2] is a UIToolbarButton with tag [0]
View [2] is a UIView with tag [3]
subview count=2
      subview [0] is a UIActivityIndicatorView with tag [31]
      subview [1] is a UILabel with tag [32]

这个问题似乎并没有出现在iPhone上,只有iPad。我已经检查了所有我表演的地方 if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) 这些逻辑似乎都没有任何意义。