Does instant replay even work??

There are many problems with instant replay in both college football and the NFL. The flaws are accepted because the end result is that they get the call right. The only problem is they DON’T! 

Nothing makes a football fan more irritated than when these situations occur ( I am a Dolphins fan, but I consider myself pretty level headed, and I am pretty objective when watching games). This weekend, in the fourth quarter with a 3 point lead over the Packers. Sparano and company decide to go for it on a 4^th and 1. They were at about the 27 yard line of Green Bay. Ronnie Brown bangs it up inside then bounces outside puts his hand on the ground, lunges forward and reaches a yard across the first down line. 

Inexplicably, the officials mark him short of the first down by about three inches. Naturally, the Dolphins challenge the spot because it is pretty clear he gained the first down. They leave the offense on the field for that very reason. Then, the referee comes out on the field and says the ruling on the field stands. http://www.nfl.com/gamecenter/2010101700/2010/REG6/dolphins@packers#tab:watch  

Well, it’s bound to happen, they screw up from time to time, right? Nope. This situation had already occurred twice that weekend in NCAA games. A review of the Texas vs Nebraska game and the Arkansas vs. Auburn game will provide you with two different plays that were wrongly called, reviewed, and left unchanged.

How does this happen? I understand how an official can miss a call when watching the play live with bodies all over the place and everything moving extremely fast. It is human nature that some of the calls will not be correct on the field. Replay was instituted for the sole purpose of assisting the officials with current technology that would make sure the call was correct. Well, that seems to not be the case anymore so let’s try to figure out how these errors happen.

Is the technology so bad where the ref in the booth doesn't have access to the same replays we the viewer are shown?

Is the wording of the rule “indisputable evidence” interpreted differently by each official?

Are referees reluctant to change a call benefiting the road team because they are afraid of the home fan’s reactions?

Is the replay official in the booth so old and decrepit that he just flips a coin and goes with it?

I don’t have the answer. But I wish the sports media wouldn’t ignore this problem. I have yet to hear a major sports show address this issue. Why won’t the media talk about this? More importantly, why does it keep happening? This is a serious problem that needs to be addressed. We all know one play or bad call can change the outcome of a game. It can change the course of a season in some cases. There is no excuse for incorrect calls to stand even after being subject to replay review.
Please add your comment below if you have an idea or explanation