No it did not change anything.
I copied also the Library folder to my desktop and ensure about permissions, change the configuration to point on this new folder and ask for a rescan at next start up. Same problem.
At this stage the library browser is nor really usable on my system.
I have to go now to the pet shop (it is Sunday
), and after if you are interested I can make some more tests and eventually share the screen (via skype or mikogo). I can also install qcad on a other PC (XP professional) if you find it could be of any interest.