Hi Christoph, Latest update: I got Kwant test working on a virtual box with lubuntu. I think I may have had a broken Vbox update when going to 4.3.20, and thus decided to install the 4.2.28 branch. That I think is anecdotical and the point was to first completely remove the old version before installing the new one -auto update was broken, thus the manual update. But that might not be all. The crash with Debian was when installing. However, I've noticed some issues when installing Guest Additions (Vbox cpu% goes +100% without the the guest OS doing nothing, and it seems to eat quite some memory as well). With guest-kernel panic included when rebooting after Guest Add's install. Booting my guest lubuntu in recovery mode and from there into resuming boot, went fine and I think it's ok again now. So, not sure what happened but I think I do have now a virtual box with kwant running. Another time I'll deal with the MUMPS libs. I don't mind solving these issues; the real frustrating thing is just how much time these things may consume. Again, thanks a lot for your support. Regards, Pol