It turns out that my program isn't working because the ATL COM DLL that the other guys created isn't correctly inserting itself into the DLL chain with the result that none of the MFC resources (like say, our strings DLL) are available to the DLL or any of the DLLs that it's calling into. It seems that I need to invoke a bit of MFC magic to get the thread that contains the CWinApp object to initialize its module state correctly.
Unfortunately, I haven't quite figured out the correct incantation.
I recognize that this is complete mumbo jumbo to most of you; sadly, it appears to have been the same to the rest of our development team or this would already be working.
For the moment, I'm deferring this problem to tomorrow and heading home.