MapView EXC_BAD_ACCESS (SIGSEGV) and KERN_INVALID_ADDRESS

I'm having some 'issues' with my application... well, it crashes in an UIViewController that is presented modally, there the user enters information through UITextFields and his location is tracked by a MapView. Lets call this view controller "MapViewController"

When the user submits the form, I call a different ViewController - modally again - that processes this info and a third one answers accordingly, then go back to a MenuVC using unwinding segues, which then calls MapViewController and so on. This sequence is repeated many times, but it always crashes in MapViewController.

Looking at the crash log, I think that the MapView can be the problem of this or some element in the UI (because of the UIKit framework). I tried to use NSZombie in order to track a memory issue but it doesn't give me a clue about whats happening.

Here is the crash log

  Hardware Model:      iPad3,4
  Process:         MyApp [2253]

  OS Version:      iOS 6.1.3 (10B329)
  Report Version:  104

  Exception Type:  EXC_BAD_ACCESS (SIGSEGV)
  Exception Codes: KERN_INVALID_ADDRESS at 0x00000044
  Crashed Thread:  0

  Thread 0 name:  Dispatch queue: com.apple.main-thread
  Thread 0 Crashed:
  0   IMGSGX554GLDriver                 0x328b9be0 0x328ac000 + 56288
  1   IMGSGX554GLDriver                 0x328b9b8e 0x328ac000 + 56206deallocated instance
  2   IMGSGX554GLDriver                 0x328bc2f2 0x328ac000 + 66290
  3   IMGSGX554GLDriver                 0x328baf44 0x328ac000 + 61252
  4   libGPUSupportMercury.dylib        0x370f86be 0x370f6000 + 9918
  5   GLEngine                          0x34ce8bd2 0x34c4f000 + 629714
  6   GLEngine                          0x34cea30e 0x34c4f000 + 635662
  7   GLEngine                          0x34c8498e 0x34c4f000 + 219534
  8   GLEngine                          0x34c81394 0x34c4f000 + 205716
  9   VectorKit                         0x3957f4de 0x394c7000 + 754910
  10  VectorKit                         0x3955552e 0x394c7000 + 582958
  11  VectorKit                         0x394d056e 0x394c7000 + 38254
  12  VectorKit                         0x394d0416 0x394c7000 + 37910
  13  VectorKit                         0x394cb7ca 0x394c7000 + 18378
  14  VectorKit                         0x394c9804 0x394c7000 + 10244
  15  VectorKit                         0x394c86a2 0x394c7000 + 5794
  16  QuartzCore                        0x354a07a4 0x35466000 + 239524
  17  QuartzCore                        0x354a06fc 0x35466000 + 239356
  18  IOMobileFramebuffer               0x376f8fd4 0x376f4000 + 20436
  19  IOKit                             0x344935aa 0x34490000 + 13738
  20  CoreFoundation                    0x33875888 0x337e9000 + 575624
  21  CoreFoundation                    0x338803e4 0x337e9000 + 619492
  22  CoreFoundation                    0x33880386 0x337e9000 + 619398
  23  CoreFoundation                    0x3387f20a 0x337e9000 + 614922
  24  CoreFoundation                    0x337f2238 0x337e9000 + 37432
  25  CoreFoundation                    0x337f20c4 0x337e9000 + 37060
  26  GraphicsServices                  0x373ad336 0x373a8000 + 21302
  27  UIKit                             0x3570e2b4 0x356b7000 + 357044
  28  MyApp                         0x000ea12e 0xe9000 + 4398
  29  MyApp                         0x000ea0e4 0xe9000 + 4324

I think thats all, additionally, I would like to ask you: if you are using unwind segues then you are releasing view controllers from the memory heap, right? Meanwhile, performing segues let you instantiate those controllers. Technically, MenuVC should be the only VC alive in the heap during the app life cycle if you understand me.