The topic of the debate was "Muhammad in the Bible?" Our opponents pointed to several passages in the Bible that supposedly refer to Muhammad. When my partner and I showed that these same passages call Jesus the Son of God, or refer to his death by crucifixion, or in other ways contradict Islam, the Muslim team was forced to claim that the Bible has been corrupted! So they were stuck insisting simultaneously that the Bible supports Islam and that the Bible has been corrupted whenever it doesn't support Islam!
Interestingly, when a Muslim says that the Bible has been corrupted, he's contradicting his own revelations. While Muslims today often claim that the Bible has been corrupted, the Qur'an says something completely different. In the Qur'an, Allah affirms the inspiration (3:3-4), preservation (6:114-115; 10:94; 18:27) and authority (5:47; 5:68) of the Christian scriptures.
This puts Muslims in a dilemma, as the following clips show.