Upgrade failed

[gtacs]

Hi all,
I have been running Ubuntu 11.03, when I signed on last night I got a message asking to upgrade to 12.(something). I hit the upgrade and let it do its thing. The comp. froze up during the installation process, now when i go to the bootloader and select the shell I want to load, it says it invalid, and opens a maintenance shell.
I am very new to linux, and any help would be appreciated.

Thanks

[dino99]

you might repair from recovery mode:

https://wiki.ubuntu.com/RecoveryMode

note: if you let the system alone to upgrade, always deactivate the screensaver and other powersaving settings, otherwise you get trouble as you hit