I'm in the process of running the 12.04 upgrade (Kubuntu). My root partition is a bit small, but I cleared as much as I could after the upgrade told me it needed more space.
During "Installing the upgrades" it was doing something with 'nvidia_current' and ran out of space writing /lib/modules/3.2.0-24-generic/updates/dkms/nvidia_current.ko
I have cleared some more space by deleting old logs, but the upgrade process sits there adding more dots to a long line. There is about 180MB free now, which seems to be going down slowly.
Will it ever continue or will a reboot continue the upgrade?