if the intake holes are anywhere close to the exhaust fan, it will render the fan practically useless. it will basically just be sucking in air through those hole(s) and blowing it right back out... leaving your cpu out in the cold... er, heat.
to keep this kind of thing from happenening, always keep air moving out the back and coming into the front. intake fans aren't necessary, so you don't really need any in the front. just make sure all holes in the back are either taped up or have a fan blowing hot air out of them. outside air will find it's way in through the front.