I am creating an invoice with multiple invoice items.
The challenge is setting the InvoiceLineQuantity field.
The query below will work if I remove the InvoiceLineQuantity field.
When I add InvoiceLineQuantity to the query; it returns the error below:

INSERT INTO InvoiceLine (CustomerRefListID, RefNumber, InvoiceLineItemRefListID, InvoiceLineDesc, InvoiceLineRate, InvoiceLineAmount, InvoiceLineSalesTaxCodeRefListID, BillAddressAddr1, BillAddressAddr2, BillAddressCity, BillAddressState, InvoiceLineQuantity, FQSaveToCache)
VALUES ('120001-1149263930', '22334', '40000-1149254278', 'Blue Hats Desc', 1.0, 5.21, '20000-1147458012', '8557 Oak Ave.', '#343', 'Berkley', 'Michigan', 3, 0)
 
Error Message
Run-time error ‘-21474672559(800004005)

[QODBC] Error parsing complete XML return string
2006-06-05 16:14:31 QODBC Ver:  6.00.00.155 *********************************************************************************************************************
IsAService: False
SQL Statement: INSERT INTO InvoiceLine (CustomerRefListID, RefNumber, InvoiceLineItemRefListID, InvoiceLineDesc, InvoiceLineRate, InvoiceLineAmount, InvoiceLineSalesTaxCodeRefListID, BillAddressAddr1, BillAddressAddr2, BillAddressCity, BillAddressState, InvoiceLine
Quantity, FQSaveToCache) VALUES ('120001-1149263930', '22334', '40000-1149254278', 'Blue Hats Desc', 1.0, 5.21, '20000-1147458012', '8557 Oak Ave.', '#343', 'Berkley', 'Michigan', 3, 0) Driver for QuickBooks\Optimizer
Error parsing complete XML return string (8)
Input XML:
<?xml version="1.0" encoding="ISO-8859-1"?>
<?qbxml version="5.0"?>
<QBXML>
    <QBXMLMsgsRq onError = "continueOnError" responseData = "includeAll">
        <InvoiceAddRq requestID = "1">
            <InvoiceAdd defMacro = "TxnID:235854ED-2C1D-4C83-B1B5-EC0D7B8C81CC">
                <CustomerRef>
                    <ListID>120001-1149263930</ListID>
                </CustomerRef>
                <RefNumber>22334</RefNumber>
                <BillAddress>
                    <Addr1>8557 Oak Ave.</Addr1>
                    <Addr2>#343</Addr2>
                    <City>Berkley</City>
                    <State>Michigan</State>
                </BillAddress>
                <InvoiceLineAdd>
                    <Amount>5.21</Amount>
                    <SalesTaxCodeRef>
                        <ListID>20000-1147458012</ListID>
                    </SalesTaxCodeRef>
                    <ItemRef>
                        <ListID>40000-1149254278</ListID>
                    </ItemRef>
                    <Desc>Blue Hats Desc</Desc>
                    <Quantity>3.00000</Quantity>
                </InvoiceLineAdd>
            </InvoiceAdd>
        </InvoiceAddRq>
    </QBXMLMsgsRq>
</QBXML>

Without doing a lot of testing, the most likely cause for the error is that InvoiceLineQuantity is in the wrong place (and doesn't add up). The Intuit qbXML SDK requires the insert columns to be in the same order as the table which is:-

SELECT InvoiceLine.TxnID, InvoiceLine.TimeCreated, InvoiceLine.TimeModified, InvoiceLine.EditSequence, InvoiceLine.TxnNumber, InvoiceLine.CustomerRefListID, InvoiceLine.CustomerRefFullName, InvoiceLine.ClassRefListID, InvoiceLine.ClassRefFullName, InvoiceLine.ARAccountRefListID, InvoiceLine.ARAccountRefFullName, InvoiceLine.TemplateRefListID, InvoiceLine.TemplateRefFullName, InvoiceLine.TxnDate, InvoiceLine.TxnDateMacro, InvoiceLine.RefNumber, InvoiceLine.BillAddressAddr1, InvoiceLine.BillAddressAddr2, InvoiceLine.BillAddressAddr3, InvoiceLine.BillAddressAddr4, InvoiceLine.BillAddressCity, InvoiceLine.BillAddressState, InvoiceLine.BillAddressPostalCode, InvoiceLine.BillAddressCountry, InvoiceLine.ShipAddressAddr1, InvoiceLine.ShipAddressAddr2, InvoiceLine.ShipAddressAddr3, InvoiceLine.ShipAddressAddr4, InvoiceLine.ShipAddressCity, InvoiceLine.ShipAddressState, InvoiceLine.ShipAddressPostalCode, InvoiceLine.ShipAddressCountry, InvoiceLine.IsPending, InvoiceLine.IsFinanceCharge, InvoiceLine.PONumber, InvoiceLine.TermsRefListID, InvoiceLine.TermsRefFullName, InvoiceLine.DueDate, InvoiceLine.SalesRepRefListID, InvoiceLine.SalesRepRefFullName, InvoiceLine.FOB, InvoiceLine.ShipDate, InvoiceLine.ShipMethodRefListID, InvoiceLine.ShipMethodRefFullName, InvoiceLine.Subtotal, InvoiceLine.ItemSalesTaxRefListID, InvoiceLine.ItemSalesTaxRefFullName, InvoiceLine.SalesTaxPercentage, InvoiceLine.SalesTaxTotal, InvoiceLine.AppliedAmount, InvoiceLine.BalanceRemaining, InvoiceLine.Memo, InvoiceLine.IsPaid, InvoiceLine.CustomerMsgRefListID, InvoiceLine.CustomerMsgRefFullName, InvoiceLine.IsToBePrinted, InvoiceLine.CustomerSalesTaxCodeRefListID, InvoiceLine.CustomerSalesTaxCodeRefFullName, InvoiceLine.SuggestedDiscountAmount, InvoiceLine.SuggestedDiscountDate, InvoiceLine.InvoiceLineType, InvoiceLine.InvoiceLineSeqNo, InvoiceLine.InvoiceLineGroupTxnLineID, InvoiceLine.InvoiceLineGroupItemGroupRefListID, InvoiceLine.InvoiceLineGroupItemGroupRefFullName, InvoiceLine.InvoiceLineGroupDesc, InvoiceLine.InvoiceLineGroupQuantity, InvoiceLine.InvoiceLineGroupIsPrintItemsInGroup, InvoiceLine.InvoiceLineGroupTotalAmount, InvoiceLine.InvoiceLineGroupSeqNo, InvoiceLine.InvoiceLineTxnLineID, InvoiceLine.InvoiceLineItemRefListID, InvoiceLine.InvoiceLineItemRefFullName, InvoiceLine.InvoiceLineDesc, InvoiceLine.InvoiceLineQuantity, InvoiceLine.InvoiceLineRate, InvoiceLine.InvoiceLineRatePercent, InvoiceLine.InvoiceLinePriceLevelRefListID, InvoiceLine.InvoiceLinePriceLevelRefFullName, InvoiceLine.InvoiceLineClassRefListID, InvoiceLine.InvoiceLineClassRefFullName, InvoiceLine.InvoiceLineAmount, InvoiceLine.InvoiceLineServiceDate, InvoiceLine.InvoiceLineSalesTaxCodeRefListID, InvoiceLine.InvoiceLineSalesTaxCodeRefFullName, InvoiceLine.InvoiceLineOverrideItemAccountRefListID, InvoiceLine.InvoiceLineOverrideItemAccountRefFullName, InvoiceLine.FQSaveToCache, InvoiceLine.FQPrimaryKey, InvoiceLine.CustomFieldInvoiceLineOther1, InvoiceLine.CustomFieldInvoiceLineOther2, InvoiceLine.CustomFieldInvoiceLineColor, InvoiceLine.CustomFieldInvoiceLineMaterial, InvoiceLine.CustomFieldInvoiceLineGroupOther1, InvoiceLine.CustomFieldInvoiceLineGroupOther2, InvoiceLine.CustomFieldInvoiceLineGroupColor, InvoiceLine.CustomFieldInvoiceLineGroupMaterial, InvoiceLine.CustomFieldInvoiceLineGroupLineOther1, InvoiceLine.CustomFieldInvoiceLineGroupLineOther2, InvoiceLine.CustomFieldInvoiceLineGroupLineColor, InvoiceLine.CustomFieldInvoiceLineGroupLineMaterial, InvoiceLine.CustomFieldOther, InvoiceLine.CustomFieldBDay, InvoiceLine.CustomFieldContract, InvoiceLine.CustomFieldSpousesName
FROM InvoiceLine InvoiceLine

So try:

INSERT INTO InvoiceLine (CustomerRefListID, RefNumber, BillAddressAddr1,
BillAddressAddr2, BillAddressCity, BillAddressState,
InvoiceLineItemRefListID, InvoiceLineDesc, InvoiceLineQuantity,
InvoiceLineRate, InvoiceLineAmount, InvoiceLineSalesTaxCodeRefListID, FQSaveToCache)
VALUES ('120001-1149263930', '22334', '8557 Oak Ave.',
'#343', 'Berkley', 'Michigan',
'40000-1149254278', 'Blue Hats Desc', 3,
1.0, 3.0, '20000-1147458012', 0)

That did the trick!

Thanks!