If one reads this CNN story, it seems pretty clear that Abdallah Higazy was up to no good. The Assistant US Attorney had him arrested for, on September 11th, having an aviation radio, staying in a hotel across the street from the World Trade Centers, and for being Arab. None of these are crimes, of course, but the attorney said that all of this was "a potentially quite significant part" of the 9/11 investigation and had him charged with making false statements. Tying him into the events of 9/11 was, obviously, part of the reason behind the arrest.
It turns out, however, that he did not have an aviation radio, he did not lie about having a radio, and even though the FBI was on a great fishing expedition arresting everybody it could, he had nothing to do with 9/11. He spent a month in jail... enough time for the FBI to force a confession out of him. To do this, it seems the FBI threatened Higazy's family's safety.
This is a case that we all know about. It's long past time that the government release the names of everybody it took into custody after 9/11 and the reasons they were arrested. Long past time.