DLL Link Error

I created a simple DLL and attempted to include it in a test app by including the header file for the functions I wished to use and linking with the .lib file created by MSVC upon compiling the DLL. When I compile the program it has no errors but when I link it I get "tri5.lib : fatal error LNK1136: invalid or corrupt file". I can't figure out what is wrong as MSVC created the lib file. Any advice? A quick response would be much appreciated as I need this project to work ASAP.

Check all project configs and rebuild the app. If that doesn't help, I don't know. But sometimes the linker just gets confused.