United States v. Love, __ F.3d __, 2005 WL 3164303 (5th Cir. Nov. 29, 2005) (court can order that a defendant pay unpaid restitution previously ordered as part of a sentence by another federal court in another federal case).
http://caselaw.lp.findlaw.com/data2/circs/5th/0430944cr0p.pdf