I got a compiled error but can't figure out why and how to fix it. Would anyone have any idea for following error message and what is it mean?

c:\program files\microsoft visual studio\vc98\include\comip.h(690) : error C2227: left of '->QueryInterface' must point to class/struct/union
        c:\program files\microsoft visual studio\vc98\include\comip.h(75) : see reference to function template instantiation 'long __thiscall _com_ptr_t<class _com_IIID<struct ADODB::_Connection,&struct __s_GUID _GUID_00000550_0000_0010_8000_00aa006
d2ea4> >::_QueryInterface(const enum TransType &)' being compiled
FlightDataDb.cpp
c:\program files\microsoft visual studio\vc98\include\comip.h(690) : error C2227: left of '->QueryInterface' must point to class/struct/union
        c:\program files\microsoft visual studio\vc98\include\comip.h(75) : see reference to function template instantiation 'long __thiscall _com_ptr_t<class _com_IIID<struct ADODB::_Connection,&struct __s_GUID _GUID_00000550_0000_0010_8000_00aa006
d2ea4> >::_QueryInterface(const enum TransType &)' being compiled
Generating Code...
Error executing cl.exe.

ContactDbGenTool.exe - 2 error(s), 0 warning(s)

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Thank you in advance.