This is completely unverified, but the LA Times refuses to publish the tape or transcript so we're left with speculation and unfounded rumors floating around the web:
Saw a clip from the tape. Reason we can't release it is because statements Obama said to rile audience up during toast. He congratulates Khalidi for his work saying "Israel has no God-given right to occupy Palestine" plus there's been "genocide against the Palestinian people by Israelis."
It would be really controversial if it got out. Tha's why they will not even let a transcript get out.