It's not an issue of MAX232 / levels or something. Everything works perfect with a Standard PC, but there are Notebooks (ie my DELL Latitude), that produce an active positive level whenever the COM port is not open, perhaps due to power saving. I assume this disturbes the Autobaud routine in the ATMEL processor. What I did with the little circuit, is prevent a long positif level to be short circuited, and as soon as there is a negativ level starts to release this short. This did the trick. Took me a while to sort everything out.

I also think there might be other applications, that will not work correct, if you use them with a notebook showing this behaviour, normally it would produce a framing error.

Werner