I have Windows XP on my hard dive and I had Ubuntu 12.04 there too. I also had Kubuntu 12.04 installed since it was first released. Recently I added a PPA to get a KDE update. I was able to successfully get several updates over time. Recently however when I installed an update KDE booted to a black screen. In trying to figure out what was wrong, neither Ubuntu or Kubuntu would boot. After just a few seconds they would return to the login screen.
I decided to re install Kubuntu 12.04 but not Ubuntu. I did but had no touchpad on my laptop and the soundcard was giving a message saying "dummy output. I can use the mouse so that problem is not a big deal but no sound is a major problem for me because of how I use my computer. I installed Kubuntu 12.10 to replace 12.04 but I had the same problems.
My original installation of 12.04 worked fine so I don't know why I had problems with the re installation. Anybody have an answer to my sound problems? My laptop is a Compaq R3275US. I'm not sure how to tell what soundcard I have.