NEW YORK (Bloomberg) - Investors in Fairfield Sentry Ltd., a feeder fund for Bernard Madoff’s Ponzi scheme, asked a judge to withhold approval from Irving Picard’s $4 billion settlement with bankrupt funds related to the Fairfield Greenwich Group, which had a Bermuda investnment management subsidiary.The deal struck by the trustee liquidating Madoff’s firm, who dropped $4 billion in claims in return for lower claims by the funds on the Madoff estate, may obstruct their own efforts to recoup losses, they said in a court filing on Thursday.