Comment 19 for bug 526379

Confirmed - I also had this problem - correct username/password would return me to the gdm welcome screen. Installing gnome-session as per comment #18 fixed the issue - so this package is for some reason left out of the dist-upgrade.

I upgraded 9.10 to lucid on my HP Mini 5101 (i386) thus:
   sudo sed -i s/karmic/lucid/g /etc/apt/sources.list
   sudo apt-get dist-upgrade