当我没有 iAd 时，我的应用程序运行良好。一旦我显示 iAd，系统就会关闭我的应用程序，因为 iAd 无法及时恢复。
我该如何解决这个问题？
Elapsed total CPU time (seconds): 1.380 (user 0.880, system 0.500), 14% CPU
Elapsed application CPU time (seconds): 0.000, 0% CPU
Thread 0:
0 libSystem.B.dylib 0x00000c98 mach_msg_trap + 20
1 libSystem.B.dylib 0x00002d64 mach_msg + 44
2 AppSupport 0x0001009e CPDMMessage + 158
3 AppSupport 0x0000f3e4 -[CPDistributedMessagingCenter _sendMessage:userInfoData:oolKey:oolData:makeServer:receiveReply:nonBlocking:error:] + 848
4 AppSupport 0x0000ed76 -[CPDistributedMessagingCenter _sendMessage:userInfo:receiveReply:error:toTarget:selector:context:nonBlocking:] + 618
5 AppSupport 0x0000deba -[CPDistributedMessagingCenter _sendMessage:userInfo:receiveReply:error:toTarget:selector:context:] + 58
6 AppSupport 0x0000e08e -[CPDistributedMessagingCenter sendMessageName:userInfo:] + 34
7 iAd 0x00012bcc -[ADSession sendMessageName:userInfo:] + 100
8 iAd 0x00013cfe -[ADSession open] + 22
9 iAd 0x000065c2 -[ADBannerView sessionDidBecomeAvailable:] + 38
10 iAd 0x00014d60 -[ADSessionManager considerCreatingSessions] + 416
11 iAd 0x00014a42 __-[ADSessionManager sessionForRecipient:]_block_invoke_1 + 34
12 libSystem.B.dylib 0x000d597c _dispatch_call_block_and_release + 12
13 libSystem.B.dylib 0x000d69f4 _dispatch_main_queue_callback_4CF + 212
14 CoreFoundation 0x00027894 __CFRunLoopRun + 1328
15 CoreFoundation 0x00027270 CFRunLoopRunSpecific + 224
16 CoreFoundation 0x00027178 CFRunLoopRunInMode + 52
17 GraphicsServices 0x000045ec GSEventRunModal + 108
18 GraphicsServices 0x00004698 GSEventRun + 56
19 UIKit 0x0000411c -[UIApplication _run] + 396
20 UIKit 0x00002128 UIApplicationMain + 664
21 StockTwits 0x00002c5c main (main.m:14)
22 StockTwits 0x00002c2c start + 32