the test version did the trick :-)
RAW works, variable bitrate seems to work (I can see the bitrate beeing calculated while shooting. How do I check if the resulting AVI is variable bitrate?)
Camera stays in "C" after <alt>
AND ... switching of partitions works like a charm!!
The Camera FW is still 1.00H. CHDK seem to be made for 1.00I. Do you know of issues from that?