The chain of causality cannot extend backwards infinitely. This would create a paradox. If there was an infinite chain of cause/effects, then it would take an infinite amount of time to arrive at the present. An infinite chain of events cannot be formed by successive addition, and the flow of time is a form of successive addition. The present moment of time is the sum of all previous moments if time. Therefore the Universe had a beginning. And the beginning itself had to be before causality, before time itself. It had to be an eternal (not the same as infinite!) uncaused cause.
wrong wrong wrong.
First off, a big misapplication of zenons paradox. you assume a linear time coordinate for starters. Read up on some GR and especially the solutions to einsteins field equations around a black hole, then you will see that funky things DO happend to the time coordinate that kindof mess up your argument.
Second, a lot of confusion about causality. Causality is NOT something you can just assume and then go around prooving things, you can build theories with closed time loops, etc.
Thirdly, the last part of your argument is really strange. It has to be eternal? how do you define eternal without a time coordinate? what about other more exotic coordinates that this event may have 'happened' in?. Just because its uncharted teritories, you cant assume that its full of pink unicorns.
I has often met the attitude from (nonprofessional) philosophers that physics and mathematics wouldnt really work without smart guys thinking and really 'understanding' the foundation, but in my oppinion science and mathematics (today) do that pretty well, and infact drive the philosophy on science (GR, quantum mechanics, principia mathematica and goedels theorem, baysian foundation on physics are good examples) rather than the other way around.
When creationists are so keen to turn the existence of god into a philosophical question (rather than a physical or a result of some logical theory constructed for that purpose) I personally think its because creationists have realized that whenever they discuss with knowlegeable people in those fields they tend to loose. Philosophy, on the other hand, just require you to say wierd and complicated things without really backing it up by experiments and calculations. See the "law of causality" as an example.