Comment 7 for bug 1168866

At least for me it's almost certainly cause the CPU is non-PAE. I remember not being able to install the 12.10 version cause it didn't support non-PAE CPUs so I installed 12.04 and hoped I could upgrade it to 12.10, but apparently the new linux image is the part that doesn't support non-PAE CPUs, not just the instalation of the whole 12.10 system.
I guess given that non-PAE CPUs are not supported anymore I'll just have to stick with the current 3.2.0-40 linux image.