Using MSI via COM in C++

Okay, so I'm trying to write a simple MFC app that allows a novice user to open an MSI package, and view some properties, ultimately for the purpose of changing some text strings.

I'm using COM and after I create my Installer object, I'm able to do some basic stuff such as InstallerPtr->GetVersion() (retrieves version of Windows Installer). Where my problem lies is in opening and actual MSI database. I have been unable to get a call to InstallerPtr->OpenDatabase() to work. I've searched the web for info (MSDN is not helpful on this, it simply tells me the parameters, and then gives me a VBS example). Here is what I'm doing in a nutshell, can you spot anything wrong (I'm leaving out error checking to keep this brief):

InstallerPtr pInstaller;
pInstaller.CreateInstance( "WindowsInstaller.Installer" );
InstallerPtr->GetVersion() // this works
_variant_t dbMode;
dbMode.intVal = 1; // msiOpenDatabaseModeTransact
DatabasePtr dbOject = pInstaller->OpenDatabase( "myapplication.msi", dbMode );

OpenDatabase throws a COM error every time, and I can't seem to get a meaningful error message from it. Also, any attempt to call LastErrorRecord (which according to MSDN can be called if OpenDatabase() fails) results in an exception.

Long day. Frustrated. Probably missing something obvious. If you can push me in the right direction I would be most grateful.

Chris

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