Problem of disable method in win32_networkadapter

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C++

Windows

Hi, I have a problem of disable method in win32_networkadapter
Here's my code:

hre = pSvc->GetObjectW(TEXT("Win32_NetworkAdapter"),
		0, NULL, &pClass, NULL);
      ....................
      hre = pClass->GetMethod(TEXT("Disable"), 0, &pMethod, NULL);
      ......................
      hre = pMethod->SpawnInstance(0, &pInInst);

the GetMethod returns successful, but the pointer pMethod is NULL, so the program crashed when calling spawninstance

I'm using vs2005 on win7

Did someone know what's wrong?

thanks!

and sorry for my English!