I have a new Toshiba qosmio x870 and for the past one week I have been trying to install Ubuntu 12.04 from a USB and Live CD without success. I keep on getting this error:

Boot failure: a proper digital signature was not found. One or more files on the selected boot device was rejected by the Secure Boot feature.

I even tried installing Ubuntu with the Windows installer. After installation and I reboot the PC, first I see the error that points to:

ubuntuwinbootwubildr.mbr

Status: 0xc000007b

Info: The OS couldn't be loaded because a required file is missing or contains errors.

When I restart, that the previous error doesn't show up and I see both Windows 8 and Ubuntu (happy that I was successful) but when I click on Ubuntu, it flags an error. This is the first time I'm having a Secure Boot-capable PC. What will be the danger in disabling the secure boot? I'll be happy if I can get assistance from anyone.