[MonoTouch] Any idea what could cause this crash?

[René Ruppert]

Hi,

>From one out of hundred taps on a UIButton, I get the following crash. There
is no managed crash.
Hitting the button starts a new thread and that thread updates the UI by
using InvokeOnMainThread(). I was able to verify that it never crashes if I
do not use a separate thread.
What line is the key line here? What is nil/null? As I can see table view
cells showing up in the crash, I assume it has to do with those.
I posted this stacktrace on SO a while ago and Rolf answered that the key is
at (4) but I've been unable to fix the problem.
Giving code is hard because I don't know what part of is causing the
problem.
Can I assume that something was setting a background color (8) and then it
crashed at (4)? Then I would be able to limit it to places where the
background color gets changed by me.

Native stacktrace:

	0   BrainloopBrowser                    0x00094fbc
mono_handle_native_sigsegv + 284
	1   BrainloopBrowser                    0x0000be72
mono_sigsegv_signal_handler + 178
	2   libsystem_c.dylib                   0x9401859b _sigtramp + 43
	3   ???                                 0xffffffff 0x0 + 4294967295
	4   QuartzCore                          0x04176891 -[CALayer
actionForKey:] + 89
	5   QuartzCore                          0x0417982d
_ZL12actionForKeyP7CALayerPN2CA11TransactionEP8NSString + 82
	6   QuartzCore                          0x0417c9c3
_ZN2CA5Layer12begin_changeEPNS_11TransactionEjRP11objc_object + 131
	7   QuartzCore                          0x04182ac1
_ZN2CA5Layer6setterEj12_CAValueTypePKv + 141
	8   QuartzCore                          0x04172ca4 -[CALayer
setBackgroundColor:] + 62
	9   UIKit                               0x021e2992
-[UIView(Internal) _setBackgroundCGColor:withSystemColorName:] + 1516
	10  UIKit                               0x021dbca5
-[UIView(Hierarchy) _setBackgroundColor:] + 145
	11  UIKit                               0x021dda06
-[UIView(Rendering) setBackgroundColor:] + 40
	12  CoreFoundation                      0x0113b51d __invoking___ +
29
	13  CoreFoundation                      0x0113b437 -[NSInvocation
invoke] + 167
	14  UIKit                               0x025c53a5
TaggingAppearanceGeneralSetterIMP + 1137
	15  UIKit                               0x02388523 -[UITableViewCell
_updateSeparatorContent] + 478
	16  UIKit                               0x02390e53 -[UITableViewCell
layoutSubviews] + 2681
	17  UIKit                               0x021e3322
-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 178
	18  CoreFoundation                      0x011d6e72 -[NSObject
performSelector:withObject:] + 66
	19  QuartzCore                          0x0417392d -[CALayer
layoutSublayers] + 266
	20  QuartzCore                          0x0417d827
_ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 231
	21  QuartzCore                          0x04103fa7
_ZN2CA7Context18commit_transactionEPNS_11TransactionE + 377
	22  QuartzCore                          0x04105ea6
_ZN2CA11Transaction6commitEv + 374
	23  QuartzCore                          0x041059d3
_ZN2CA11Transaction14release_threadEPv + 65
	24  libsystem_c.dylib                   0x94009e0c
_pthread_tsd_cleanup + 85
	25  libsystem_c.dylib                   0x93fc264c _pthread_exit +
146
	26  libsystem_c.dylib                   0x93fc29a0 pthread_exit + 33
	27  BrainloopBrowser                    0x0020434e thread_exit + 30
	28  BrainloopBrowser                    0x00203d03
thread_start_routine + 163
	29  BrainloopBrowser                    0x001aeb20 gc_start_thread +
80
	30  libsystem_c.dylib                   0x93fc0ed9 _pthread_start +
335
	31  libsystem_c.dylib                   0x93fc46de thread_start + 34