I was thinking about it... In "One Of Them" when the clock hit zero and all the symbols started popping up and we all hear that wierd sound like there was a major lockdown about to occur something hit me. A few episodes back Locke and Micheal discovered that there were blast doors in the hatch. I think this has a mahor significance to my idea. Just maybe when the clock hits zero and all those symbols appear again the Hatch will shut its blast doors and something will launch from the island. An emergency procedure or something. In the Dharma orientation video when Dr.Marvin Candle said that they will try to avoid another incident so all prosedure must be followed. This is related to my theory.

__________________
"You Don't Even Know What Your Running From!"-Jack