Send Array of Bytes to serial port

Question

I'm am struggeling with the following issue. I need to send multiple Bytes to a serial port. Seems pretty easy and I don't know if I have tomatoes on my eyes, but I can't get it to work. Sending single bytes is working fine, generating an array manually with multiple Hex-values as bytes works fine too. But converting a String to an array of bytes doesn't work.

Here is my simplyfied code:

send(ByVal sCommand as String, ByVal sComPort as String, ByRef sRetStr as String, ByVal lTimeout as long)
    Dim lStopWatch as Stopwatch
    lStopWatch.Reset()
    lStopWatch.Restart()
    sRetStr = ""
    'In this example sCommand contains "UJB3A01019221043"        

    Try    
        comObject as System.IO.Ports.SerialPort = New System.IO.Ports.SerialPort
        comObject.PortName = sComport
        comObject.BaudRate = 115200
        comObject.DataBits = 8
        comObject.StopBits = 1
        comObject.Handshake = IO.Ports.Handshake.None
        comObject.Parity = IO.Ports.Parity.None
        comObject.WriteTimeout = 1000
        comObject.ReadTimeout = 1000
        comObject.Encoding = System.Text.Encoding.GetEncoding(1252)
        comObject.Open()
        
        Dim ByteArray(sCommand.Length-1) as Byte            'sCommand contains the mentioned string
        ByteArray = System.Text.Encoding.ASCII.GetBytes(sCommand)

        comObject.DiscardInBuffer()
        comObject.Write(ByteArray, 0, ByteArray.Length)     'in this case, the receiving device fails and i dont get any answere
        
        ByteArray = {&H55, &H4A, &H42, &H33, &H41, &H30, &H31, &H30, &H31, &H39, &H32, &H32, &H31, &H30, &H34, &H33}
        comObject.Write(ByteArray, 0, ByteArray.Length)     'this works fine and i receive 0x55 as answere, but i dont understand the difference
                                                            'between the manually generated ByteArray and ByteArray = System....GetBytes(sCommand)

        Do
            System.Threading.Thread.Sleep(10)
            if comObject.BytesToRead >0 Then
                sRetStr &= comObject.ReadByte.ToString("x2")
            End If
            Application.DoEvents()
        Loop While(lStopWatch.ElapsedMilliseconds < lTimeout Or sRetStr.StartsWith(CStr(sCommand(0))))
        send = True
    Catch ex as Exception
        sRetStr = ex.Message.toString()
        send = False
    End Try
End Function

I appreciate every kind of useful help.

By the way, I HAVE to use VB 2010 express,... I know, I know, but I have no other choice...