i fail to understand these 2 crash reports - ios

Question

Since i received comments of crashes but the app never crashes for me, I now use critterism to hunt down crashes.
I received one report that pointed to me to an error by me. It was easy, since the method name was given and i
could look in my code what might crash. So far, so good.
But i also have the following two that puzzle me.
To me it looks like the app crashes in some internal apple library.( Most likely due to me feeding it some broken stuff...)
There is no call from my code in the crash, so where do start looking?
Does anyone understand these crashes?
Any idea how i can catch these and maybe get some more crash info?
No.1:
0 CoreFoundation 0x3585f88f __exceptionPreprocess + 162
1 libobjc.A.dylib 0x37c06259 objc_exception_throw + 32
2 CoreFoundation 0x35862a9b -[NSObject doesNotRecognizeSelector:] + 174
3 CoreFoundation 0x35861915 ___forwarding___ + 300
4 CoreFoundation 0x357bc650 _CF_forwarding_prep_0 + 48
5 UIKit 0x332f3efb -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 546
6 UIKit 0x332f2f39 -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 916
7 UIKit 0x332f2763 -[UITableView layoutSubviews] + 206
8 UIKit 0x33296f37 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 182
9 CoreFoundation 0x357be1fb -[NSObject performSelector:withObject:] + 42
10 QuartzCore 0x3268eaa5 -[CALayer layoutSublayers] + 216
11 QuartzCore 0x3268e6bd _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 216
12 QuartzCore 0x32692843 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 226
13 QuartzCore 0x3269257f _ZN2CA11Transaction6commitEv + 314
14 QuartzCore 0x326ba911 _ZN2CA11Transaction5flushEv + 44
15 QuartzCore 0x326ba8e3 +[CATransaction flush] + 34
16 UIKit 0x332a1fb1 _afterCACommitHandler + 52
17 CoreFoundation 0x35833b1b __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 18
18 CoreFoundation 0x35831d57 __CFRunLoopDoObservers + 258
19 CoreFoundation 0x358320b1 __CFRunLoopRun + 760
20 CoreFoundation 0x357b54a5 CFRunLoopRunSpecific + 300
21 CoreFoundation 0x357b536d CFRunLoopRunInMode + 104
22 GraphicsServices 0x37451439 GSEventRunModal + 136
23 UIKit 0x332c1cd5 UIApplicationMain + 1080
24 Wohnungssuche 0x000d5218 start + 40
No. 2:
Thread: Unknown Name (Crashed)
0 libobjc.A.dylib 0x35beb5d0 objc_msgSend + 16 + 15
1 UIKit 0x39fb0541 -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 409 + 408
2 UIKit 0x39f95361 -[UITableView(_UITableViewPrivate) _updateVisibleCellsNow:] + 1317 + 1316
3 UIKit 0x39fac7ff -[UITableView layoutSubviews] + 207 + 206
4 UIKit 0x39f68897 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 259 + 258
5 QuartzCore 0x34ab74eb -[CALayer layoutSublayers] + 215 + 214
6 QuartzCore 0x34ab708d _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 461 + 460
7 QuartzCore 0x34ab7fb1 _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 17 + 16
8 QuartzCore 0x34ab799b _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 239 + 238
9 QuartzCore 0x34ab77ad _ZN2CA11Transaction6commitEv + 317 + 316
10 QuartzCore 0x34aee7df _ZN2CA7Display11DisplayLink8dispatchEyy + 255 + 254
11 QuartzCore 0x34aee6d9 _ZN2CA7Display16IOMFBDisplayLink8callbackEP21__IOMobileFramebufferyyyPv + 65 + 64
12 IOMobileFramebuffer 0x375f0fd7 IOMobileFramebufferVsyncNotifyFunc + 155 + 154
13 IOKit 0x3282a5ad IODispatchCalloutFromCFMessage + 193 + 192
14 CoreFoundation 0x3918288b __CFMachPortPerform + 119 + 118
15 CoreFoundation 0x3918d3e7 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 35 + 34
16 CoreFoundation 0x3918d38b __CFRunLoopDoSource1 + 139 + 138
17 CoreFoundation 0x3918c20f __CFRunLoopRun + 1383 + 1382
18 CoreFoundation 0x390ff23d CFRunLoopRunSpecific + 357 + 356
19 CoreFoundation 0x390ff0c9 CFRunLoopRunInMode + 105 + 104
20 GraphicsServices 0x3344933b GSEventRunModal + 75 + 74
21 UIKit 0x39fb9291 UIApplicationMain + 1121 + 1120
Thanks for your help!

Answer 1

The crash point in both cases is the same:
UIKit 0x39fb0541 -[UITableView(UITableViewInternal) _createPreparedCellForGlobalRow:withIndexPath:] + 409 + 408
In the first case, the table view was trying to call a method on an instance that does not implement said method. The second crash was caused by trying to message garbage.
Thus, the most likely conclusion is that both crashes are symptoms of a single problem; you have an object that is being prematurely released or over-released.
In particular, your table view's data source is being released before or while a table is reloading.
I suspect that UITableView is trying to call the data source's method to create a cell. You could confirm this by setting a breakpoint on said method and looking at the stack trace. If my bet is correct, you'll see the _createPreparedCellForGlobal... method in the trace.
Without knowing details of your app, hard to say. Most likely, this is timing related issue between data being loaded on the screen and the user doing something that causes a request to be canceled earlier than the table view is done loading, causing your data source to be deallocated out from under the table (which can happen because the table view has an assign reference to your object; a non-retaining reference).
To try and reproduce, focus on:
• slow network connection or variable bandwidth (if your app is client/server)
• do things the user might do that causes operations to cancel
• quickly navigate between views without waiting for the update to complete drawing
In your comments, you mention that you are trying on "two different iPhones". Try on other device types and across different network configurations.