Weird BIT Behavior...

I'm seeing some strange behavior from a stored procedure of mine. It essentially grabs a bunch of rows using a fairly simple JOIN....here's the from statement:




Code Snippet
FROM Payment PY (NOLOCK)
JOIN (SELECT DISTINCT
PY.AccountPaymentId,
ROW_NUMBER() OVER(ORDER BY PY.AccountPaymentId ASC) AS RowNum
FROM Payment PY (NOLOCK)) AS SQ
ON (SQ.AccountPaymentId = PY.AccountPaymentId)
INNER JOIN Payee PE ON PE.PayeeId = PY.PayeeId INNER JOIN
Party PT ON PE.PartyId = PT.PartyId INNER JOIN
Distribution DS ON PY.DistributionId = DS.DistributionId LEFT OUTER JOIN
Account AC ON DS.AccountId = AC.AccountId INNER JOIN
clm CM ON PE.clm_no = cm.clm_no LEFT OUTER JOIN
PartyAddress PA ON PY.PartyAddressId = PA.PartyAddressId AND
PT.PartyId = PA.PartyId
WHERE RowNum BETWEEN (((@Page * @PageSize) - @PageSize) + 1) AND ((@Page * @PageSize) - @PageSize) + @PageSize
and ((@PayeeName IS NULL) OR (PT.[Name] LIKE '%' + @PayeeName + '%'))
AND ((@AccountId IS NULL) OR (AC.AccountId = @AccountId))
AND ((@DistributionId IS NULL) OR (DS.DistributionId = @DistributionId))
AND ((@PaymentDate IS NULL) OR (DATEADD(day, DATEDIFF(day, 0, PY.PaymentDate), 0) = DATEADD(day, DATEDIFF(day, 0, @PaymentDate), 0))) -- Ignores the time
AND ((@PaymentNumber IS NULL) OR (PY.AccountPaymentId = @PaymentNumber))
AND ((@IsReconciled IS NULL) OR (PY.ReconciledInd = @IsReconciled))
AND ((@AmountIssued IS NULL) OR (PY.PaymentAmount = @AmountIssued))
AND ((@AmountPaid IS NULL) OR (PY.AccountPaidAmount = @AmountPaid))
AND ((@IssueStatus IS NULL) OR (PY.PaymentStatusEnumItemId = @IssueStatus))
AND ((@AccountStatus IS NULL) OR (PY.AccountStatusEnumItemId = @AccountStatus))
AND ((@IsReissued IS NULL) OR (PY.ReissuedInd = @IsReissued))
ORDER BY AccountPaymentID ASC


When I pass a 1 for the @IsReconciled parameter, I get the right number of rows back - 9779. But when I pass a 0 (zero), i get no rows back, although there are 222 rows which satisfy the condition.

Is there somethig I'm overlooking (I don't think I am...)? I don't know whay 1 works and 0 wouldn't...

FYI - the @IsReconciled parameter is set to NULL at the outset of the procedure -

@IsReconciled Bit = Null