Thanks Alan and Julien for spending the time to clarify the issue. I should perhaps explain why I ran into this mess.
I used to work with LyX1.6.3, than decided to update to 1.6.5 using svn (I kept 1.6.3, call lyx165 for the update). Now I thought I could profit from the new features of the LyX2 trunk, but did not want to risk to muddle up my 1.6.5. So I thought I could do it in a similar way as with 1.6.5, calling lyx2 But Julien is warning: > Use either command, not both. You then will see the tree of the lyx > source files being downloaded to your lyx-devel folder. Once you have > the code, you can do with it as you please. What you probably want to > do, is compile the code. So what I will do now is installing the 2.X.X on my notebook and try it out there. It takes, however, some time, since I installed Debian on it and have difficulties with the screen modus. Thanks, especially for the step by step guide of Julien Wolfgang