I was having this same login loop problem starting on 9-15-10 in Kubuntu Maverick Beta too, but since after installing the Ubuntu daily-live cd dated 21-sep-2010 (plus the installing the kubuntu-desktop meta-package), the login loop problem appears to be fixed. I have also tested and installed the Kubuntu daily-live cd dated 22-sep-2010 and the problem appears to be fixed there too. I use 32 bit systems.
I was having this same login loop problem starting on 9-15-10 in Kubuntu Maverick Beta too, but since after installing the Ubuntu daily-live cd dated 21-sep-2010 (plus the installing the kubuntu-desktop meta-package), the login loop problem appears to be fixed. I have also tested and installed the Kubuntu daily-live cd dated 22-sep-2010 and the problem appears to be fixed there too. I use 32 bit systems.