John, I am not sure if this will help but I found a discussion on this type of behavior when you try to statically link to the MFC, however it was not for LabVIEW 7.0. You may be able to get around the error by linking to the MFC dynamically rather than statically. Another option may be to use LoadLibrary and GetProcAddress to dynamically load and call the function. Lastly you could use the VC delayload feature to make the LV DLL not get loaded until the first call is made into it. See VC help on "delayload" for information on setting this up.
If none of these help I would suggest seeing if you can get the same behavior with a very simple LabVIEW DLL and MFC project. If that works I would start looking at where you are calling the LabVIEW DLL, to see if you can narrow it down. Evan National Instruments
