Thief,
I don't know whether you've heard this type of argument before (if you've read Hume or Kant or any Theravadin scholars then you probably have), but here goes:
If omnipotence and a beginningless and endless existence are the attributes of a god, then it would appear than the existence of such a being is not possible.
If we wish for an omnipotent god who created the known universe, then this god must also have created the very concept of existence (the existence/non-existence duality), which we know so well as one of the underlying features of what we call space-time. But if we say that god created spacetime and therefore existence itself, then what do we mean when we say that this god "always existed", or that he/she existed before the universe was created?
The suggestion that something existed before the dawn of existence itself is nonsense, unless we allow for some other reality, some "external" universe with its own space-time, where god existed before the creation of our universe, where the creation of our universe was initiated, and where existence/nonexistence were already possibilities.
But if we propose this as a solution, we strip god of omnipotence, as we place him under the constraints of this other universe and its conditions. We are also avoiding the problem, because if god existed before he created our "bubble" of logical and physical laws, then he did it within the confines and rules of some other, larger "bubble" with it's own laws, which must exist beyond the outer edge of our bubble. In this way we can keep trying to displace god to the "outer universe", and run into the same problem every time: we simply subject god to the rules of another, more distant and external location.
In this way, by insisting on god's divine attributes, we deny him existence. And if we insist that he exists, we are forced to deny his "godliness". In this way, logic makes the existence of a god impossible.