QuickBooks error message: The transaction is empty.

My example:

c = QB::Check.new
c[{
  :IsToBePrinted => false,
  # :RefNumber => "10",
  :AccountRef => {:FullName => "Case Checking TechRockstars"},
  # :Total => "2000.00",
  :Address => { :Addr1 => "Rigo Gutierrez",
                :Addr2 => "1703 E. Charlinda St.",
                :City => "West Covina",
                :State => "CA",
                :PostalCode => "91791"},
  :TxnDate => Time.now.to_date.to_s,            
  :PayeeEntityRef => {:FullName => "Rigo Gutierrez"},  
  :Memo => "Blah",
  :ExpenseLine => [{
    :Amount => "2000",
    :AccountRef => { :FullName => "Advertising and Promotion"},
    :CustomerRef => { :FullName => "Rigo Gutierrez"}}]
  
  # :AppliedToTxn => { :PaymentAmount => "2000"}
}]

Copyied from console:

>> c = QB::Check.new
=> <Check:#18937120
  >
>> c[{
?>   :IsToBePrinted => false,
?>   # :RefNumber => "10",
?>   :AccountRef => {:FullName => "Case Checking TechRockstars"},
?>   # :Total => "2000.00",
?>   :Address => { :Addr1 => "Rigo Gutierrez",
?>                 :Addr2 => "1703 E. Charlinda St.",
?>                 :City => "West Covina",
?>                 :State => "CA",
?>                 :PostalCode => "91791"},
?>   :TxnDate => Time.now.to_date.to_s,            
?>   :PayeeEntityRef => {:FullName => "Rigo Gutierrez"},  
?>   :Memo => "Blah",
?>   :ExpenseLine => [{
?>     :Amount => "2000",
?>     :AccountRef => { :FullName => "Advertising and Promotion"},
?>     :CustomerRef => { :FullName => "Rigo Gutierrez"}}]
>>   
?>   # :AppliedToTxn => { :PaymentAmount => "2000"}
?> }]
=> {
     :Address=>{
       :City=>"West Covina",
       :PostalCode=>"91791",
       :State=>"CA",
       :Addr1=>"Rigo Gutierrez",
       :Addr2=>"1703 E. Charlinda St."},
     :AccountRef=>{:FullName=>"Case Checking TechRockstars"},
     :Memo=>"Blah",
     :ExpenseLine=>[
       {:Amount=>"2000",
         :AccountRef=>{:FullName=>"Advertising and Promotion"},
         :CustomerRef=>{:FullName=>"Rigo Gutierrez"}}
     ],
     :PayeeEntityRef=>{:FullName=>"Rigo Gutierrez"},
     :IsToBePrinted=>false,
     :TxnDate=>"2009-07-21"
   }
>> c.save
Quickbooks::QuickbooksAPIError: #3180: There was an error when saving a Check.  QuickBooks error message: The transaction is empty.
    from /Library/Ruby/Gems/1.8/gems/quickbooks-0.9.9/lib/quickbooks.rb:134:in `execute'
    from /Library/Ruby/Gems/1.8/gems/quickbooks-0.9.9/lib/quickbooks/model.rb:404:in `save'
    from /Library/Ruby/Gems/1.8/gems/quickbooks-0.9.9/lib/quickbooks/model.rb:403:in `catch'
    from /Library/Ruby/Gems/1.8/gems/quickbooks-0.9.9/lib/quickbooks/model.rb:403:in `save'
    from (irb):486
>> q.debug
=> "6.0"
>> c.save
=> "<?xml version=\"1.0\" ?>
<?qbxml version=\"6.0\" ?>
<QBXML>
  <QBXMLMsgsRq onError=\"stopOnError\">
    <CheckAddRq>
      <CheckAdd>
        <AccountRef>
          <FullName>Case Checking TechRockstars</FullName>
        </AccountRef>
        <PayeeEntityRef>
          <FullName>Rigo Gutierrez</FullName>
        </PayeeEntityRef>
        <TxnDate>2009-07-21</TxnDate>
        <Memo>Blah</Memo>
        <Address>
          <Addr1>Rigo Gutierrez</Addr1>
          <Addr2>1703 E. Charlinda St.</Addr2>
          <City>West Covina</City>
          <State>CA</State>
          <PostalCode>91791</PostalCode>
        </Address>
        <IsToBePrinted>false</IsToBePrinted>
      </CheckAdd>
    </CheckAddRq>
  </QBXMLMsgsRq>
</QBXML>"
>>

Example from SDK:

<?xml version="1.0" ?> 
<?qbxml version="2.0"?> 
<QBXML> 
  <QBXMLMsgsRq onError="stopOnError"> 
    <CheckAddRq> 
      <CheckAdd> 
        <AccountRef> 
          <FullName>Checking</FullName> 
        </AccountRef> 
        <PayeeEntityRef> 
          <FullName>Barley, Renee</FullName> 
        </PayeeEntityRef> 
        <TxnDate>2007-12-15</TxnDate> 
        <Memo>Refund for overpayment</Memo> 
        <IsToBePrinted>1</IsToBePrinted> 
        <ExpenseLineAdd> 
          <AccountRef> 
            <FullName>Accounts Receivable</FullName> 
          </AccountRef> 
          <Amount>100.00</Amount> 
          <CustomerRef> 
            <FullName>Barley, Renee</FullName> 
          </CustomerRef> 
        </ExpenseLineAdd> 
      </CheckAdd> 
    </CheckAddRq> 
  </QBXMLMsgsRq> 
</QBXML>