Ok, I did what you said and everything was ok. It was something I did, but I run the first time an upgrade directly.
This time, I install first, then, replace the new database tables by the old ones and did the upgrade. No database errors.
Now, I have another problem (sorry!) :
I can't see any picture or thumbnails in my gallery, I only have the name. but if I do a right click on the image title and choose "Display image / show image" (I'm not sure of the firfox translation, I don't have an english version) then, my image is displayed (I mean, the path is good) and if I go back, then, it is displayed well in the gallery.
I can see the cause of that: I import the gallery database, but the users are still not imported from the old forum: their is no user in
vb database except some test users. Do you think the problem come from here?