I forgot to say that the installation was made with a USB key which was created with Unetbootin.
I tested some more cases: - Installing 6.0.3 netinstall i386 in a virtualbox, and it comes with Gnome - I made another USB key with "cat debian.iso > /dev/sdX" (so no Unetbootin) and installation comes with Gnome. So I still can reproduce the problem with the USB key created with unetbootin, but I just cannot explain it. Why using unetbootin makes that ... maybe not a debian bug afterall ;) -- Sébastien
