Can you give us some info on your computer? What brand&model is it? How big is your HDD&RAM?
What are the specific ("actual") errors coming up when you boot/install/etc...
I had a problem installing 11.04/10.10/10.04/etc on my one desktop. Turns out it didn't have enough RAM to run the installer right. Plus, having unsupported hardware with no drivers didnt help me any, either.
Anything you can tell us will help greatly.
You said you had access to the shell.. Awesome!
$ sudo fsck -l
$ sudo lshw
The first gives us a little info about your HDD, and the second tells us more about your computer in general.