Long answer:
"The administration does not want the victims of Sept. 11 interfering with its foreign policy," says Peter M. Leitner, director of the Washington Center for Peace and Justice (WCPJ). Leitner says the Bush administration may be concerned that if other victims of the Sept. 11 attacks also filed lawsuits and won civil-damage awards it would reduce Iraqi resources that the administration wants to use to rebuild the country. Leitner and others say this explains Bush's reticence at this time to report the convincing evidence linking Saddam and al-Qaeda that has been collected by U.S. investigators and private organizations seeking damages. "The [Bush] administration is intentionally changing the topic," claims Leitner, and sidestepping the issue that "Iraq has been in a proxy war against the U.S. for years and has used al-Qaeda in that war against the United States."
My theory has been all along that they were waiting to hand power over to the Iraqis before letting this info out due to possible lawsuits against Iraq. Maybe they reassessed the situation and feel comfortable releasing this now. Any lawyer that filed a suit now would be laughed out of court as the Iraqis were victims of Saddam themselves and cannot be held responsible for his past transgressions.
It was ravingnutter's post I was referring to in my reply #64. Good answer, ravingnutter.