I just got a Toshiba S855 (i7-3630QM) machine, with Windows 8 pre-installed, and have been through a nightmare to make it work alongside Ubuntu 12.10.
Making it dual boot was not the issue, after I found the proper instructions on how to deal with the UEFI stuff. The problem came after having it boot into Ubuntu; at first the OS booted fine, but after installing the recommended updates, the screen just went crazy; only a small frame at the top, flickering, and no access to text-mode screens either.
After booting into recovery mode, I found that X was reporting a problem accessing the ATI card's VBIOS, resulting in a 'No Screen Found' error.
I tried nearly everything I found around ... removing fglrx*; reinstalling the linux headers after or before fglrx; used the ATI drivers; used the OpenSource drivers; to no avail.
After 3 or 4 reinstallations, I found that the issue is being caused by the latest kernel image suggested by the update manager. The USB image I used for installing came with 3.5.0-17, and the update manager suggested 3.5.0-26. So what I did was to lock the former version in Synaptic, applying all updates but the kernel update, and Ubuntu is working like a charm now.
I'm aware that maybe having an outdated kernel is not the best solution, but it was the only way I found to make it work.
So, can anyone out there confirm that there are issues with the latest suggested kernel updates and ATI Radeon cards? The (horrible) downside on Toshiba machines is that the built-in Intel GPU is not accessible, so no way of switching over to Intel graphics.
Is there an easy way to go back to a previous kernel image after reinstalling a new one? I know that old entries are kept in GRUB, but in my case, after installing 3.5.0-26, even booting into 3.5.0-17 did not worked well ... same screen freeze issue.
How can I know if 13.04 will break my install?
Any light on this will be appreciated.