title: The iphone app crash when closed and run again, what is reason?
body: <p>My app is working ok at the first time, but when I terminated it(close background instance also) and run again, the app has been crashed and this raised this log:</p>
  
  <pre><code>Elapsed total CPU time (seconds): 19.560 (user 19.000, system 0.560), 98% CPU 
  Elapsed application CPU time (seconds): 19.000, 95% CPU
  
  Thread 0:
  0   libobjc.A.dylib                 0x33479482 0x33476000 + 13442
  1   JdP                             0x0001a478 0x1000 + 103544
  2   libobjc.A.dylib                 0x33479888 0x33476000 + 14472
  3   libobjc.A.dylib                 0x3347f526 0x33476000 + 38182
  4   libobjc.A.dylib                 0x3347bf32 0x33476000 + 24370
  5   libobjc.A.dylib                 0x3347977a 0x33476000 + 14202
  6   libobjc.A.dylib                 0x334794b0 0x33476000 + 13488
  7   JdP                             0x0005c4c0 0x1000 + 373952
  8   JdP                             0x0000406c 0x1000 + 12396
  9   JdP                             0x00003e42 0x1000 + 11842
  10  UIKit                           0x320a0270 0x32062000 + 254576
  11  UIKit                           0x320acd04 0x32062000 + 306436
  12  UIKit                           0x320acb74 0x32062000 + 306036
  13  UIKit                           0x320aca72 0x32062000 + 305778
  14  UIKit                           0x320ac54a 0x32062000 + 304458
  15  UIKit                           0x320ac358 0x32062000 + 303960
  16  UIKit                           0x320ac29c 0x32062000 + 303772
  17  UIKit                           0x320ac238 0x32062000 + 303672
  18  UIKit                           0x320750c8 0x32062000 + 78024
  19  CoreFoundation                  0x33a5ebb8 0x33a20000 + 256952
  20  QuartzCore                      0x3410867e 0x340f9000 + 63102
  21  QuartzCore                      0x34108436 0x340f9000 + 62518
  22  QuartzCore                      0x34102566 0x340f9000 + 38246
  23  QuartzCore                      0x3410237c 0x340f9000 + 37756
  24  QuartzCore                      0x3410ce48 0x340f9000 + 81480
  25  QuartzCore                      0x34109b6e 0x340f9000 + 68462
  26  UIKit                           0x320ac038 0x32062000 + 303160
  27  UIKit                           0x3209a310 0x32062000 + 230160
  28  UIKit                           0x32066484 0x32062000 + 17540
  29  UIKit                           0x32065ec2 0x32062000 + 16066
  30  UIKit                           0x32065900 0x32062000 + 14592
  31  GraphicsServices                0x33b0eefc 0x33b0a000 + 20220
  32  CoreFoundation                  0x33a556f8 0x33a20000 + 218872
  33  CoreFoundation                  0x33a556bc 0x33a20000 + 218812
  34  CoreFoundation                  0x33a47f76 0x33a20000 + 163702
  35  CoreFoundation                  0x33a47c80 0x33a20000 + 162944
  36  CoreFoundation                  0x33a47b88 0x33a20000 + 162696
  37  UIKit                           0x32099302 0x32062000 + 226050
  38  UIKit                           0x32096e8c 0x32062000 + 216716
  39  JdP                             0x00002cbc 0x1000 + 7356
  40  JdP                             0x00002c70 0x1000 + 7280
  
  Thread 1:
  0   libSystem.B.dylib               0x33b89974 0x33b5c000 + 186740
  1   libSystem.B.dylib               0x33c33704 0x33b5c000 + 882436
  2   libSystem.B.dylib               0x33c33174 0x33b5c000 + 881012
  3   libSystem.B.dylib               0x33c32b98 0x33b5c000 + 879512
  4   libSystem.B.dylib               0x33bd724a 0x33b5c000 + 504394
  5   libSystem.B.dylib               0x33bcf970 0x33b5c000 + 473456
  
  Thread 2:
  0   libSystem.B.dylib               0x33b5d268 0x33b5c000 + 4712
  1   libSystem.B.dylib               0x33b5f354 0x33b5c000 + 13140
  2   CoreFoundation                  0x33a48648 0x33a20000 + 165448
  3   CoreFoundation                  0x33a47ed2 0x33a20000 + 163538
  4   CoreFoundation                  0x33a47c80 0x33a20000 + 162944
  5   CoreFoundation                  0x33a47b88 0x33a20000 + 162696
  6   WebCore                         0x304df124 0x30428000 + 749860
  7   libSystem.B.dylib               0x33bd6886 0x33b5c000 + 501894
  8   libSystem.B.dylib               0x33bcba88 0x33b5c000 + 457352
  
  Unknown thread crashed with unknown flavor: 5, state_count: 1
  </code></pre>
  
  <p>I really don't know the reason and the way to debug this app, please help me!</p>