Passing a VARIANT to a COM function and returning it.

I have a C++ class that needs to get information from an oscilloscope for analysis. I have the code that issues the command to the o'scope and can see the o'scope getting the info. Here is that code:

void CbeLecroy::GetScaledWF(LCHAN channel, int numpoints, VARIANT* rvals)
{
	waveform.Attach(activeDSO->GetScaledWaveform(bCHANNEL[channel], numpoints, 0));
	rvals->parray = waveform.parray;
	float* pfloatVals;
	HRESULT hr;
	hr = SafeArrayAccessData(rvals->parray, (void**)&pfloatVals); // direct access to SA memory

	if (SUCCEEDED(hr))
	{
		long lowerBound, upperBound;  // get array bounds
		SafeArrayGetLBound(rvals->parray, 1, &lowerBound);
		SafeArrayGetUBound(rvals->parray, 1, &upperBound);

		fvec.clear();

		long cnt_elements = upperBound - lowerBound + 1;

		for (int i = 0; i < cnt_elements; ++i)  // iterate through returned values
			fvec.push_back(pfloatVals[i]);

		SafeArrayUnaccessData(rvals->parray);
	}
//	SafeArrayDestroy(psa);
}

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The calling function looks like this:

    VARIANT rvals;
	comLecroy->GetScaledWF(channel, numpoints, &rvals);

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When I breakpoint in the top function, I can see valid data in the loop:

		for (int i = 0; i < cnt_elements; ++i)  // iterate through returned values
			fvec.push_back(pfloatVals[i]);

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However, when I exit the called function and return to the calling function, I get an exception. Any ideas why?

Thanks, Brian