you dodn't have the file name for the original and patched file do you? It should be like this:
Original file: bloodgulch( the untouched bloodgulch from a different folder)
Patched file: bloodgulch(the file that you modded in the real Halo folder that you play with)
In other words the files must correspond to each other. Bloodgulch(umodded and bloodgulch modded). Just copy all of your maps that you use to play into a backup folder, but make sure that they are pure(original)(unmodded).