First thing I did was install the ppa-purge utility (see my blog post here). I then systematically checked the entries in /etc/apt/source.list and all the .list files in /etc/apt/source.list.d and purged all the PPA (Personal Package Archives) I was using and replacing them with official Karmic versions from the Ubuntu repository.
I then downloaded the ubuntu-10.04-alternate-i386.iso file from one of Ubuntu's mirror sites and following the instructions here, upgraded my setup to Ubuntu 10.04 (Lucid Lynx).
I rebooted the computer and did another update (since there are updates to some of the packages since the release on 29-Apr-2010) in a terminal shell by typing:
sudo apt-get update && sudo apt-get upgrade -y
Everything worked correctly as expected except by Plymouth. A quick Google search landed me here and my setup works exactly as expected.
I am now a happy