I have an app that runs well on iPhone 4, iPod Touch 2nd gen, iPhone 3G, but that crashes on iPod Touch 4th gen systematically after 2 or 3 memory warnings. I tested it in Instruments, and it tells me the app uses 2MB when the memory warning is sent. This seems to be a very small amount of memory.
I suspect a problem related with the UIWebView and I wander if Instruments actually shows the amount of memory used by UIWebView. 2MB is not enough to generate memory warnings on the previous apps I've been working on.
It's not a leak in UIWebView as I have the crash sometimes at the first time I show an UIWebView.