Thanks for the cheatcode hint. I will try that.

There is another thing I tried in the meantime: I installed an Knoppix 5.0 (form the aforementioned older Live cd that does start) to an old an small hdd testwise - with knx2hdd in the console. That worked fine. I tried to lower te resolution for the monitor to 800x600 (the monitor is pretty old and small, although it does feature colours and runs now with a scan rate of 85 hz). The scan rate was set to 75 hz should be fine: system crashed, - black screen, the system offered to start a new session.

I can get hold of a better monitor and I will try that too, but with your remark about high speed marginal burns in mind..., maybe I should order a cd or something and try that. It just does not make sense that all my new Live Distributions don´t want to start...Thanks for your help