Power Line has video and details. Here's an excerpt from the L.A. Times (no link because the Times site pointers seem busted):

Jim Gilchrist, the Aliso Viejo accountant who co-founded the Minuteman Project, was forced offstage seconds into his speech at Columbia University on Wednesday night by students who said his anti-illegal immigration message was not welcome in New York.

Gilchrist, who was invited by the Columbia University College Republicans, was unharmed but was unable to continue speaking as planned and was forced to leave the stage after an altercation with students....

The Columbia melee began after two students rushed from behind the stage toward Gilchrist and unrolled a banner that read in Spanish, English and Arabic, "No One Is Illegal."

Seeing the two, others in the audience ran toward the stage, including about two dozen who managed to get onto the 3-foot-high platform, past security guards and ropes, where Gilchrist was only a few words into his speech.

The lectern was knocked over and Gilchrist fell back, smashing his reading glasses....

No one was arrested. The incident was videotaped and shown on TV newscasts....

Oh, and here's a lovely quote from one of the "protest" participants, Columbia junior Ryan Fukumori (a board member of the Columbia Asian American Alliance and treasurer of the Columbia International Socialist Organization:

These are racist individuals heading a project that terrorizes immigrants on the U.S.-Mexican border .... They have no right to be able to speak here.

Here's a statement from Columbia's President, Lee Bollinger (who is also a noted First Amendment scholar):

President Lee C. Bollinger's Statement on Freedom of Speech October 6, 2006, 4:30 p.m.

Columbia University has always been, and will always be, a place where students and faculty engage directly with important public issues. We are justifiably proud of the traditions here of intellectual inquiry and vigorous debate. The disruption on Wednesday night that resulted in the termination of an event organized by the Columbia College Republicans in Lerner Hall represents, in my judgment, one of the most serious breaches of academic faith that can occur in a university such as ours.

Of course, the University is thoroughly investigating the incident, and it is critically important not to prejudge the outcome of that inquiry with respect to individuals. But, as we made clear in our University statements on both Wednesday night and Thursday, we must speak out to deplore a disruption that threatens the central principle to which we are institutionally dedicated, namely to respect the rights of others to express their views.

This is not complicated: Students and faculty have rights to invite speakers to the campus. Others have rights to hear them. Those who wish to protest have rights to do so. No one, however, shall have the right or the power to use the cover of protest to silence speakers. This is a sacrosanct and inviolable principle.

It is unacceptable to seek to deprive another person of his or her right of expression through actions such as taking a stage and interrupting the speech. We rightly have a visceral rejection of this behavior, because we all sense how easy it is to slide from our collective commitment to the hard work of intellectual confrontation to the easy path of physical brutishness. When the latter happens, we know instinctively we are all threatened.

We have extensive University policies governing the actions of members of this community with respect to free speech and the conduct of campus events. Administrators began identifying those involved in the incident as it transpired and continue to investigate specific violations of University policies to ensure full accountability by those found to be responsible.

University personnel are also evaluating event management practices that are specifically intended to help event organizers, participants and protestors maintain a safe environment in which to engage in meaningful and sometimes contentious debate across the spectrum of academic and political issues. These are some of the many steps we intend to take in the weeks ahead to address this matter in our community.

Let me reaffirm: In a society committed to free speech, there will inevitably be times when speakers use words that anger, provoke, and even cause pain. Then, more than ever, we are called on to maintain our courage to confront bad words with better words. That is the hallmark of a university and of our democratic society. It is also one of our central safeguards against the impulses of intolerance that always threaten to engulf our commitment to proper respect for every person.

I'm pleased to see this response, and I hope it will be followed up with suitable action against the thugs.

Thanks to commenter Micah for the pointer to the statement.