If memory serves me, he was just ticked off about US troops on Saudi soil. He said they had defiled Mecca and Medina by being there. THAT is when the whole thing started with bin Laden. If I am wrong, please correct me.
Aden hotel used by Yemen goverment hit by grenade (Reuters)
from the article: Reputed 9/11 mastermind says he decapitated journalist Daniel Pearl