Not sure what has happened here but...
I have dual boot Windows XP and ubuntu karmic.
At some point following a session using ubuntu I booted up and Windows had disappeared from the grub menu.
At this stage I could get into ubuntu. Since then, the ubuntu options (there are two kernels as options) do not work. Can't remember the exact message but the gist is that it cannot find a certain file.
So at the moment nothing boots.
I can boot to ubuntu from cd but don't know where to start diagnosing/fixing.
I am a bit of a linux noob so please be clear and explicit.