lock-free multithreaded code may lead to double-free or other unexpected results (ie. crash)
* hopefully fixes the following crash @ windows phone store:
Frame    Image           Function                    Offset        
0        ntdll.dll       RtlReportCriticalFailure    0x0000004e    
1        ntdll.dll       RtlpReportHeapFailure       0x0000001e    
2        ntdll.dll       RtlpHeapHandleError         0x00000016    
3        ntdll.dll       RtlpLogHeapFailure          0x0000005a    
4        ntdll.dll       RtlFreeHeap                 0x0004d31e    
5        MSVCR110.dll    free                        0x00000018    
6        SDLPal.exe                                  0x00018b92