I would first make sure I have my data safe, for that I would:
- download the Ubuntu ISO (www.ubuntu.com)
- burn the ISO on a cdrom with deepburner (www.deepburner.com)
- boot from the cdrom and make sure you select the boot LiveCD option (don't install Ubuntu)
- when the LiveCD Ubuntu is booted I would copy all important data to a large USB stick, probably in parts if you have a lot of data
After making sure I have all my data, I would try to find the solution to get the system working again. If all fails, reinstall.
But make sure your data is safe first, before you try any more suggestions.
Marcel EDIT: Commercial link removed
Edited by garmanma, 28 November 2009 - 10:33 AM.