From Foxnews.com (excerpt):
Meanwhile, sources close to the situation told Fox News that there was a "coincidental" link between Berg and accused Sept. 11 conspirator Zacarias Moussaoui.
FBI agents interviewed Berg a few years ago when they were investigating the Sept. 11 terrorist attacks on New York and Washington, the sources said. He was interviewed because, unbeknownst to him, Moussaoui had used his e-mail account when he was in Oklahoma.
Berg attended the University of Oklahoma and Moussaoui first settled in Norman, Okla., when he came to the U.S. The accused co-conspirator used at least one of the university's computers to communicate online, according to the sources.
The sources said that the FBI concluded that Berg had innocently given his e-mail account to someone and it had landed in the hands of other people, including Moussaoui.