I call your attention to the 20th Amendment, Section 3 which is the governing law. It provides for the possibility that a President elect (or Vice President elect) may not be able during the time after election by the Electoral College and before Inauguration to demonstrate that he is qualified (natural born citizen, age 35+, residence in US 14+ yrs) and thus would need to be replaced before Inauguration.
"If a President shall not have been chosen before the time fixed for the beginning of his term, or if the President elect shall have failed to qualify, then the Vice President elect shall act as President until a President shall have qualified; and the Congress may by law provide for the case wherein neither a President elect nor a Vice President elect shall have qualified, declaring who shall then act as President, or the manner in which one who is to act shall be selected, and such person shall act accordingly until a President or Vice President shall have qualified."
OK, if the Democrats win the electoral vote and Obama can't show that he is qualified (according to the Constitutional requirements), then as of Jan. 20, 2009, Joe Biden would become Acting President, and Congress would rush through a law changing the rules so that Obama would qualify as a natural born citizen, and then he would be sworn in as President. They would have to wait until Jan. 20 or GWB would be able to veto it.
Phillip Berg will have to live in a foreign country under an assumed name if Obama wins.