OSX AUGraph重建导致badComponentType错误

在OSX上，我正在为我的音频系统创建一个AUGraph，如下所示:

OSStatus result = NewAUGraph(&mGraph);
AUNode outputNode;
AudioComponentDescription outputDesc;
outputDesc.componentType = kAudioUnitType_Output;
outputDesc.componentSubType = kAudioUnitSubType_DefaultOutput;
outputDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
outputDesc.componentFlags = 0;
outputDesc.componentFlagsMask = 0;
result = AUGraphAddNode(mGraph, &outputDesc, &outputNode);
AUNode converterNode;
AudioComponentDescription converterDesc;
converterDesc.componentType = kAudioUnitType_FormatConverter;
converterDesc.componentSubType = kAudioUnitSubType_AUConverter;
converterDesc.componentManufacturer = kAudioUnitManufacturer_Apple;
converterDesc.componentFlags = 0;
outputDesc.componentFlagsMask = 0;
result = AUGraphAddNode(mGraph, &converterDesc, &converterNode);
result = AUGraphConnectNodeInput(mGraph, converterNode, 0, outputNode, 0);
result = AUGraphOpen(mGraph);
...initialize graph, start graph, etc...

这一切都很好，我能听到声音等。之后系统被关闭:

unsigned char isRunning = false;
AUGraphIsRunning(mGraph, &isRunning);
if (isRunning)
    AUGraphStop(mGraph);
OSStatus result;
unsigned char isInitialized = false;
AUGraphIsInitialized(mGraph, &isInitialized);
if (isInitialized)
{
    result = AUGraphUninitialize(mGraph);
}
result = DisposeAUGraph(mGraph);

同样，这里没有问题。然而，在系统重新启动时，第一个代码块再次执行后不久。:

result = AUGraphOpen(mGraph);

"result"显示为-2005 (badComponentType)。有人知道是什么引起的吗?