If everyone can smell it, then the buildup should be quite visible. Are you sure that you've looked EVERYWHERE?
Mold likes damp places with little air movement, so it's most likely in the places that are hardest to get to. You should look in the places that haven't been touched in a long time. Narrow spaces between furniture and a wall (especially if it's the outer wall) are prime places. Drawers that haven't been opened for a while (don't forget to check the bottoms of the drawer and inside the cabinet itself). Etc. If it's hard to get to - check it out.
Added: Also, a mustachian way of getting rid of the mold - wash it with vinegar! It's cheap, ecological, and kills off mold quite well. It doesn't leave a protective coating or anything though. After you've washed it off, you still need to make sure that the place gets plenty of ventilation in the future, or the mold will return in a while. Just don't forget to wear rubber gloves while handling the vinegar, or your skin will be quite unhappy for a week or two (I speak of experience :P)