Class not found - was channel definition question

I am much closer.  Tomcat is putting some key messages in the console and I overlooked them.  It looks like I am closer than I thought.  The request looks like its getting received, but my service blows up on response due to I think two class not found issues.  But, I can't tell what classes are missing.

[Flex]Deserializing AMF/RTMP request
Version: 3  null
  2.0

  (Command method=null (0) trxId=2.0)
    null
    (Externalizable Object #0 'flex.data.messages.DataMessageExt')
      (Array #1)
        [0] = (Typed Object #2 'flex.data.messages.DataMessage')
          identity = (Object #3)
            partId = 81959
          operation = 11
          correlationId = "419F99AA-B649-9490-650D-88F3CAADBCB7"
          headers = (Object #4)
          messageId = "8AF6C660-9DE3-F155-6A91-88F3CAC5A4F0"
          timestamp = 0
          destination = "DocumentPart"
          timeToLive = 0
          body = (Typed Object #5 'com.hpdocs.ds.document.DocumentPart')
            documentId = 81960
            partId = 81959
            content = "Hello World"
          clientId = "05E549ED-455F-A9AF-EEDE-88F3CA7E4BF9"
"DocumentPart"
(Object #6)
        DSEndpoint = "hp_rtmp"
        DSId = "F65B351A-A60C-6F91-2932-44630DAED2B9"
(Byte Array #7, Length 16) ""
7
[Flex]Received command: TCCommand [ Cmd: 0, MethodName: null, TrxID: 2.0]
[Flex]Serializing AMF/RTMP response
Version: 3
  (Command method=_error (0) trxId=2.0)
    (Typed Object #0 'flex.messaging.messages.ErrorMessage')
      headers = (Object #1)
      rootCause = (Typed Object #2 'java.lang.NoClassDefFoundError')
        message = "javax/transaction/SystemException"
        localizedMessage = "javax/transaction/SystemException"
        cause = (Typed Object #3 'java.lang.ClassNotFoundException')
          message = "javax.transaction.SystemException"
          localizedMessage = "javax.transaction.SystemException"
          cause = null
          exception = null
      body = null
      correlationId = "419F99AA-B649-9490-650D-88F3CAADBCB7"
      faultDetail = null
      faultString = "There was an unhandled failure on the server. javax/transaction/SystemException"
      clientId = "F65B3649-620E-C827-50C4-6A1C78BC3712"
      timeToLive = 0.0
      destination = "DocumentPart"
      timestamp = 1.273607998612E12
      extendedData = null
      faultCode = "Server.Processing"
      messageId = "F65B3675-5409-795E-747F-B2F459749415"