It sounds like you may have a 120mm fan mount. Are you measuring the same between the screws and not center to center?
EDIT.
Here is a 120mm fan with the approximate distance between the holes. Please note normally one measures to the center of each hole, but my guess is this is what you have done.
As you can see a 92mm fan will not line up with the holes in your case(not that one can not MAKE it fit).