What's wrong with the CASE statement below? I'm getting "Incorrect syntax near the keyword 'THEN'." on the last CASE.

SELECT	ab.sAmark_Bank_Desc,
		pm.sPayment_Method_Desc,
		trn.dtInsert_DT,
		trn.iTrading_Partner_ID,
		tp.sTP_Name1,
		trn.iOrder_Hdr_ID,
		t.sTrade_Type_CD,
		t.sTran_Group_CD,
		t.sPayment_Term_CD,
		trn.decTrans_Amt,
		CASE sTrans_Type_CD
			WHEN 'CR' THEN 'Cash Receipt'
			ELSE 'Cash Disbursement'
		END AS GroupDesc,
		CASE sTran_Group_CD
			WHEN 'MAR' THEN trn.decTrans_Amt
			ELSE 0
		END AS iMar,
		CASE sTran_Group_CD
			WHEN 'MAR' THEN 0
			ELSE trn.decTrans_Amt
		END AS iNotMar,

-- This statement is erroring
CASE
	WHEN (t.decTrade_Product_Balance <> 0 AND 
		 ((t.sTrade_Type_Pay_Rec = 'PAY' OR t.sTrade_Type_Pay_Rec = 'REC') 
		 AND t.sTran_Group_CD <> 'MAR') THEN trn.decTrans_Amt
	ELSE 0
END AS iProdBal


	FROM Transactions trn
	JOIN Trade t ON t.iTrade_ID = trn.iTrade_ID
	JOIN Trading_Partner tp ON tp.iTrading_Partner_ID = trn.iTrading_Partner_ID
	JOIN Payment_Method pm ON pm.sPayment_Method_CD = trn.sPayment_Method_CD
	LEFT JOIN Amark_Bank ab ON ab.sAmark_Bank_CD = trn.sAmark_Bank_CD
	WHERE trn.sTrans_Type_CD = 'CR'