Speculation:
IF the Palestinians are celebrating, that does not mean they perpetrated these terrorist acts.
Remember how many Americans cheered when Iran and Iraq were killing each other.
Furthermore, ARAFAT has denied involvement (whatever HIS word is worth).
IF the Palestinians did this, I would believe it would be the harbinger of Arafat's demise. He exists as a leader ONLY because he can affect the actions of America. Therefore, I believe it would take a challenger to Arafat, hoping to discredit him and replace him, who would make the Palestinians responsible for this.
Furthermore, the Israelis have infiltrated the Palistinian movement so completely, we would have had prior information and, (if there's a single cajone left in Washington) prevent these attacks (by political action or by force).