Hello there again,
I must be cursed. As explained before, I succeeded in having my wifi
work by switching to wheezy, following Nicolas's solution.
Then I just wanted to install Vim (gVim actually). Synaptic told me
there were tons of things to do, which I did, except it broke here and
there (on thing was that dialog [box, I suppose] was impossible
because TERM was not set, and indeed the details of progress appeared
in command-line style); update was cancelled. I started again, it
apparently progressed a little bit more, but still failed. I can't
remembered exactly what happened, but some things were related to Gnome.
Anyway, gVim was installed, but I'd lost e.g. NetworkManager in the
taskbar (although I still had an internet connection), so I thought
rebooting might be good. Alas, after rebooting, I had no desktop
anymore, simply the commandline. I updated Gnome, just in case, but
still no desktop. I launched "synaptic safe-upgrade", which did a lot
of things, but didn't gave me the desktop back, even after reboot.
So, what have I done wrong again?