Hmm, link errors look like you have different name mangling in DLL and application. Strange issue if you have rebuilt both projects with the same compiler. May be you have to do some changes to NDISAPI.DLL to build properly with MinGW. Regretfully,I have never used MinGW and I can hardly advise how to persuade it to make proper linkages.
You may consider using C interface instead C++ one, it won’t have problems like this.