EvtDTE / VCProjectEngineLibrary can't get their properties.

We have product which get information including projects, compiler flag, linker Flag.. etc from VS2003, 2005, 2008, 2010 .sln file using EvtDTE / VCProjectEngineLibrary.

And this product has been working at PC of many customer.  But I was contacted by Some of our customer who said this didn't work.

I received their .sln file, .vcxproj file and try to reappear curcumstance. But It works well at my PC.

why can't get object at their PC..?

Just in case, should have I got all source files from their and tested it?

What are things that may affect getting object from EvtDTE/ VCProjectEngineLibrary?

Failed parts is as follows:

vs 2003

			CComPtr<EnvDTE::BuildDependencies> pBuildDeps;
			CComPtr<EnvDTE::BuildDependency> pBuildDep;
			hResult = pBuildDeps->Item(CComVariant(i),&pBuildDep);
			if(FAILED(hResult)) {
				throw CS_NVIP_Exception(eNVIP_EH1,_T("Failed Getting Depedency Object."));
			}

			pPrjDepends = new CS_NVIP_PrjDependency;
			if(pPrjDepends == NULL) {
				throw CS_NVIP_Exception(eNVIP_EH3,_T("Failed Memory Allocation"));
			}

			this->m_arrDependencies.Add((CS_NVIP_IPrjDependency*)pPrjDepends);

			CComPtr<EnvDTE::Project> pBuildPrj;
			hResult = pBuildDep->get_Project(&pBuildPrj); <= Failed!!
			if(FAILED(hResult)) {
				throw CS_NVIP_Exception(eNVIP_EH1,_T("Faild Getting Project Object"));
			}

VS 2010

		CComPtr<VCLinkerTool> pLinkerTool
			VARIANT_BOOL bDelaySign = VARIANT_FALSE;

			hResult = pLinkerTool->get_DelaySign(&bDelaySign);
			if(FAILED(hResult)) { <= Failed!!
				throw CS_NVIP_Exception(eNVIP_EH1,_T("Faild Getting DelaySign."));
			}