WASHINGTON (Reuters) - The judge in the U.S. government s antitrust case against Facebook Inc said on Tuesday the social media company s motion to dismiss the lawsuit raises a number of serious challenges and put the discovery process on hold. In a brief order, Judge James Boasberg of the U.S. District Court for the District of Columbia said he expected to rule on the motion to dismiss next month. Given that Facebook s motion to dismiss raises a number of serious challenges to the complaint, the judge wrote in a brief order, it would be premature to exchange documents until he has a chance to decide if some or all of the complaint will be tossed out.